Herbicide compositions of extended soil life

ABSTRACT

Herbicidally active thiocarbamates are employed in combination with organophosphorothioates and -dithioates and -phosphonothioates, -dithioates and -trithioates, the latter in sufficient quantity to prevent soil degradation of the former. As a result, the herbicidal effectiveness of the thiocarbamate is significantly enhanced and prolonged, rendering a single application of the herbicide effective over a longer period of time. Such herbicidal compositions can optionally contain a non-phytotoxic antidotally effective amount of an amide of haloalkanoic or dihaloalkanoic acid.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part of U.S. patent application Ser. No. 507,616, filed Jun. 24, 1983; now abandoned which in turn is a continuation-in-part of U.S. patent application Ser. No. 304,216, filed Sept. 21, 1981; now abandoned which in turn is a continuation-in-part of U.S. patent application Ser. No. 198,034, filed Oct. 17, 1980, now abandoned; which in turn is a continuation of U.S. patent application Ser. No. 060,603, filed Jul. 27, 1979, now abandoned; which in turn is a continuation-in-part of U.S. patent application Ser. No. 944,094, filed Sept. 20, 1978, now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to herbicidal compositions and methods of use. In particular, this invention relates to herbicidal compositions comprising an herbicidally active thiocarbamate in combination with an organophosphorus compound, the latter serving to prolong the effectiveness of a single application of the thiocarbamate herbicide in controlling undesired plant growth.

Thiocarbamates are well known in the agricultural art as herbicides useful for weed control in crops such as corn, potatoes, beans, beets, spinach, tobacco, tomatoes, alfalfa, and others. Thiocarbamates are primarily used in pre-emergence application. They have been found to be particularly effective when incorporated into the soil prior to the planting of the crop. As a herbicide, the thiocarbamate is most concentrated immediately after its application. How long thereafter the initial concentration is retained depends in large part on the particular soil used. Thus the rate at which the thiocarbamate herbicide concentration declines following its application tends to vary from one type of soil to the next. This is evident both in the observable extent of actual weed control and in the detectable presence of undegraded thiocarbamate remaining in the soil after considerable time has elapsed.

It has now been discovered that the soil persistence of certain herbicidally active thiocarbamates is significantly extended by the incorporation of certain organophosphorus compounds, which have no herbicidal activity of their own, into the herbicide formulation. This improvement in the soil persistence of the thiocarbamate can manifest itself in a variety of ways. Improved soil persistence can be shown by herbicidal efficacy tests, wherein the degree of weed injury is measured after a set period of time following application of the herbicide. In such a test, the organophosphorus compound, which has no herbicidal activity of its own, is shown to increase the herbicidal effectiveness of the thiocarbamate by increasing the persistence of the latter in the soil, and thus prolonging its effective life. Also demonstrated herein are soil persistence test results which evidence by periodic soil analyses that the number of thiocarbamate herbicide molecules that degrade in the soil is lessened in the presence of an organophosphorus extender of this invention.

BRIEF DESCRIPTION OF THE INVENTION

This invention relates to a novel herbicidal composition comprising

(a) an herbicidally effective amount of a thiocarbamate having the formula ##STR1## in which

R¹ is C₁ -C₆ alkyl,

R² is C₁ -C₆ alkyl,

R³ is C₁ -C₆ alkyl or cyclohexyl; and

(b) an amount of an organophosphorus compound having the formula ##STR2## in which

R⁴ is C₁ -C₆ alkyl, C₃ -C₆ alkenyl, C₃ -C₆ alkynyl, or C₅ -C₇ cycloalkyl, and is optionally substituted with one or members selected from halo, cyano, C₁ -C₃ alkoxy, and C₁ -C₃ alkylthio,

R⁵ is C₁ -C₄ alkyl, C₁ -C₄ alkoxy, or C₁ -C₄ alkylthio,

R⁶ is C₁ -C₁₀ alkyl, C₂ -C₁₀ alkenyl, or C₂ -C₄ alkynyl, optionally substituted with one or more members selected from halo, nitro, cyano, C₁ -C₃ alkoxy, and C₁ -C₃ alkylthio, C₅ -C₇ cycloalkyl, or

-(R⁷)_(m) -φ in which

R⁷ is C₁ -C₄ alkyl, C₂ -C₄ alkenyl, or C₂ -C₄ alkynyl, optionally substituted with one or more members selected from halo and cyano,

m is zero or one, and

φ is phenyl or phenylthio optionally substituted with one or more members selected from halo, trifluoromethyl, cyano, nitro, C₁ -C₃ alkyl, C₁ -C₃ alkoxy, C₁ -C₃ carbalkoxy, C₁ -C₃ alkylsulfinyl, formyl, α-nitrovinyl, α-ethylthio-α-cyanovinyl, α-cyanovinyl, and α-butynyl,

X is oxygen or sulfur, and

Y is oxygen or sulfur, sufficient to extend the soil life of said thiocarbamate.

In a preferred embodiment of the invention, the compounds shown above are defined such that

R¹, R², R³ and Y are defined as above, and

R⁴ is C₁ -C₆ alkyl other than tertiary butyl, optionally substituted with halo, or is C₃ -C₆ alkenyl optionally substituted with cyano;

R⁵ is C₁ -C₄ alkyl, straight-chain C₁ -C₆ alkoxy or C1-C4 alkylthio other than tertiary butylthio;

R⁶ is C₁ -C₄ alkyl substituted with one C₁ -C₃ alkylthio group; C₅ -C₇ cycloalkyl; C₁ -C₄ alkylimino optionally usbstituted with one, two or three halogen atoms; phenyl optionally substituted with nitro, ortho-nitro and halo, C₁ -C₃ alkylsulfinyl, α-pentynyl, or trifluoromethyl; benzyl optionally substituted with halo; or is -(R⁷)-φ in which

R⁷ is C₁ -C₄ alkylene substituted with either cyano or with one, two or three halogen atoms; and φ is phenyl substituted with halo when R₇ is substituted with cyano but is phenylthio substituted with halo when R₇ is substituted with one, two or three halogen atoms;

X is oxygen or sulfur; with the provisos that:

when R⁶ is C₅ -C₇ cycloalkyl, substituted or unsubstituted phenyl, or substituted or unsubstituted benzyl, then X must be oxygen;

when R⁴ is allyl, Y is oxygen, and R⁶ is para-nitrophenyl, then R⁵ is other than methyl; and

when R⁴ methyl and R⁶ is phenyl, then R⁵ is other than C₁ -C₄

alkylthio or ethoxy; in an amount sufficient to extend the soil life of said thiocarbamate.

In a second preferred embodiment, the compounds are defined such that

R¹, R², R³ and Y are defined as above;

R⁴ is C₁ -C₆ alkyl other than tertiary butyl, optionally substituted with halo;

R⁵ is ethyl, straight-chain C₁ -C₄ alkoxy, or C₁ -C₄ alkylthio other than tertiary butylthio;

R⁶ is C₅ -C₇ cycloalkyl, benzyl or phenyl optionally substituted with either halo, ortho-nitro and halo;

X is oxygen;

with the proviso that wherein R⁴ is methyl, Y is oxygen or sulfur, and R⁶ is phenyl than R⁵ is other than C₁ -C₄ alkylthio or ethoxy.

In a third preferred embodiment, the compounds are defined such that R¹, R², R³ and Y are defined as above;

R⁴ is ethyl, n-propyl, or n-butyl;

R⁵ is methoxy, ethoxy, n-propoxy, ethylthio, or n-propylthio;

R⁶ is C₅ -C₇ cycloalkyl, benzyl or phenyl optionally substituted with halo;

X is oxygen;

with the proviso that wherein Y is sulfur, R⁴ is ethyl, n-propyl or n-butyl and R⁶ is phenyl, then R⁵ is other than methoxy.

This invention further relates to a method of controlling undesirable vegetation comprising applying the above composition to the locus where control is desired.

As used herein, the term "alkyl," "alkenyl," and "alkynyl" are intended to include both straight-chain and branched-chain radicals unless otherwise indicated. All carbon atom ranges are intended to be inclusive of their upper and lower limits.

The term "halogen atom" or "halo" is used to designate fluorine, chlorine, bromine, or iodine atoms, as well as any combination thereof.

The term "herbicide," as used herein, means a compound which adversely controls or modifies the growth of plants. By the term "herbicidally effective amount" is meant an amount of compound which causes an adverse modifying effect upon the growth of plants. By "plants" is meant germinant seeds, emerging seedlings and established vegetation, including roots and aboveground portions. Such adverse controlling or modifying effects include all deviations from natural development, for example, killing, retardation, defoliation, desiccation, regulation, stunting, tillering, stimulation, leaf burn, dwarfing and the like.

The phrase "to extend the soil life of said thiocarbamate" is used herein to denote the effect whereby herbicidal effectiveness of the thiocarbamate is maintained in substantially the same form it assumed when first applied to the locus. An extended soil life can be manifest in a slower rate of decline of weedkilling potency.

DETAILED DESCRIPTION OF THE INVENTION

According to the present invention, the above-described organophosphorus compound is added to the thiocarbamate in order to prolong the molecular integrity and herbicidal effectiveness of the latter. As the examples below indicate, there is no critical range of the ratio of these two components. The soil-life-extending effect is observable over a broad range of ratios. It is most convenient, however, to apply the compounds in a weight ratio of from about 0.1:1 to about 50:1 (thiocarbamate: organophosphorus). Preferably, the weight ratio ranges from about 1:1 to about 25:1, and most preferably from about 1:1 to about 15:1.

Examples of thiocarbamates which are useful in the present invention are S-ethyl N,N-di-n-propylthiocarbamate, S-ethyl N,N-diisobutylthiocarbamate, S-n-propyl N,N-di-n-propylthiocarbamate, S-n-propyl-N-ethyl-N-n-butylthiocarbamate, and S-ethyl-N-ethyl-N-cyclohexyl thiocarbamate.

Examples of organophosphorus compounds which are useful in the present invention are O,O-diethyl-O-phenyl phosphorothioate, O,O-diethyl-O-benzyl phosphorothioate, O-ethyl-O-phenyl-S-n-propyl phosphorodithioate, O-ethyl-S-ethyl-O-phenyl phosphorodithioate, O-ethyl-O-phenyl-S-n-butyl phosphorodithioate, O,O,-diethyl-O-cyclohexyl phosphorothioate, O,O,-diethyl-O-meta-clorophenyl phosphorothioate, O-butyl-O-methyl-O-phenyl phosphorothioate, O,O-di-n-propyl-O-phenyl phosphorothioate, O,O,-dimethyl-O-benzyl phosphorothioate, O-2-chloroethyl-O-ethyl-O-phenyl phosphorothioate, O-ethyl-O-phenyl-S-isobutyl phosphorodithioate, O-n-propyl-S-ethyl-O-phenyl phosphorodithioate, and O-phenyl-O-n-propyl-S-n-propyl phosphorodithioate. Further examples are listed in the test dat shown below.

The usefulness of many thiocarbamates as herbicides can be significantly broadened to include a wider variety of crops by the inclusion of an antidote in the herbicide formulation. The antidote protects the crop from injury by the herbicide, increasing the tolerance of the crop for the herbicide. The herbicide is thus rendered more selective in its action, retaining its potency against the undesired weeds, while showing a decreased herbicidal effect against the desired crop species. The antidotes which are especially effective in protecting crops from thiocarbamate herbicides can be described as amides of haloalkanoic acids. Such antidotes are preferably amides of dihaloalkanoic acid, such as, dichloroacetic acid. Said haloalkanoic or dihaloalkanoic acids preferably have 2 to 7 carbon atoms.

For antidote descriptions and methods of use, reference is made to U.S. Pat. No. 3,959,304, issued to Teach on May 25, 1976 ; U.S. Pat. No. 3,989,503, issued to Pallos et al. on Nov. 2, 1976; U.S. Pat. No. 4,021,224, issues to Pallos et al. on May 3, 1977; U.S. Pat. No. 3,131,509, issued to Hoffman on May 5, 1964; U.S. Pat. No. 3,564,768, issued to Hoffman on Feb. 3, 1971; U.S. Pat. No. 4,137,070, issued to Pallos et al. on Jan. 30, 1979; U.S. Pat. No. 4,294,764, issued to Rinehart on Oct. 13, 1981; U.S. Pat. No. 4,256,481, issued to Gardi et al. on May 17, 1981; U.S. Pat. No. 4,415,353, issued to Pallos et al. on Nov. 15, 1983; U.S. Pat. No. 4,415,352, issued to Pallos et al. on Nov. 15, 1983. ##STR3## in which n is 1 or 2, and R⁸ and R⁹ are independently C₁ -C₁₂ and alkyl, C₂ -C₁₂ alkenyl, C₁ -C₄ alkylene substituted with phenyl, dialkoxyalkyl wherein the alkoxy and alkyl groups each have 1-4 carbon atoms, and C₁ -C₄ alkylene substituted with a 5- to 8-membered heterocyclic ring.

Preferable embodiments of said antidotes include those wherein n is 1 or 2, R⁸ and R⁹ are independently C₁ -C₆ alkyl, C₂ -C₆ alkenyl, dialkoxyethyl, cyclic acetal or C₁ -C₂ alkylene substituted with phenyl. Further preferred embodiments include those antidotes wherein n is 2, R⁸ and R⁹ are independently C₁ -C₄ alkyl, C₂ -C₄ alkenyl, dimethoxyethyl, dioxolanylmethyl or benzyl. Examples falling within the above formul are N,N-diallyl dichloroacetamide, N,N-diallyl chloroacetamide, N-allyl-N2,2-dimethoxyethyl dichloroacetamide, N-allylN-[2-(1,3-dioxolanyl)]-methyl dichloroacetamide and 2,2-dichloro-N-ethyl-Nbenzyl acetamide.

Further useful antidotes are oxazolidines and thiazolidines having the formula ##STR4## in which R¹⁰ is C₁ -C₄ alkyl, haloalkyl, or dihaloalkyl, R¹¹, R¹², R¹³, R¹⁵ and R¹⁶ are each independently hydrogen or methyl, R¹⁴ is hydrogen, methyl or phenyl, and X is oxygen or sulfur. Examples of such antidotes include 2,2,5-trimethyl-N-dichloroacetyl oxazolidine (R¹⁰ =CHCl₂, R¹¹ =R¹² =R¹³ thiazolidine (R¹⁰ =CHCl₂ ; R¹¹ =R¹² =R¹³ =R¹⁴ =H; R¹⁵ =R¹⁶ =R¹⁷ =CH₃ ; X=O); 2,2-dimethy-N-dichloroacetyl thiazolidine (R¹⁰ =CHCL₂ ; R¹¹ =R¹² =R¹³ =R¹⁴ =H; R¹⁵ =R¹⁶ =CH₃ ; X=S); and 2,2-dimethyl-3-dichloroacetyl-5-phenyl oxazolidine (R¹¹ =R¹² =R¹³ =H; R¹⁴ =phenyl; R¹⁵ =R¹⁶ =CH₃).

Further useful antidotes are dichloroacetamide derivatives having the formula ##STR5## in which

Q is oxygen, sulfur, SO or SO₂ ;

n is 0 or 1, and

R¹⁷ and R¹⁸ are identical or different and represent hydrogen, alkyl or halophenyl, hydroxyl or nitro; or

R¹⁷ and R¹⁸ together form a butylene, pentylene or hexylene group which can be substituted with one or two methyl groups, with the proviso that if n=0, R¹⁷ and R¹⁸ are not hydrogen, alkyl or substituted phenyl.

A preferable embodiment of said antidotes include those wherein Q and n are defined as above and R¹⁷ and R¹⁸ together form an unsubstituted butylene, pentylene or hexylene ring, or a butylene, pentylene or hexylene ring substituted by 1 or 2 methyl groups. Examples of such antidotes include N-dichloroacetyl-1-oxa-5-azaspiro-(5,5)-undecan; N-dichloroacetyl-1-oxa-4-azaspiro-(4,5)-decane; N-dichloroacetyl-10-methyl-1-oxa-4-azaspiro-(4,5)-decane; N-dichloroacetyl-8-methyl-1-oxa-4-azaspiro-(4,5)-decane; N-dichloroacetyl-6,10-dimethyl-1-oxa-4-azaspiro-(4,5)-decane; N-dichloroacetyl-1-thia-4-azaspiro-(4,5)-decane; N-dichloroacetyl-1-oxa-5-azaspiro-(5,6)-dodecane; and N-dichloroacetyl-1-oxa-4-azaspiro-(4,4)-nonane.

A still further useful antidote is 1,8-naphthalic anhydride.

The antidote is applied in conjunction with the thiocarbamate and the organophosphorus compound in a nonphytotoxic antidotally effective amount. By "non-phytotoxic" is meant an amount of the antidote which causes at most minor injury to the desired crop species. By "antidotally effective" is meant an amount of the antidote which substantially decreases the extent of injury caused by the thiocarbamate to the desired crop species. The preferred weight ratio of herbicide to antidote is from about 0.1:1 to about 30:1. The most preferred weight ratio range is from about 3:1 to about 20:1.

The following examples are offered to illustrate the compositions, methods, and effectiveness of the present invention, and are not intended to limit the invention in any way.

EXAMPLE 1 Herbicidal Activity Improvement Tests

This example offers herbicidal activity test data for many representative extender compounds within the scope of this invention showing their effectiveness in improving the herbicidal activity of thiocarbamates. The effect is observed by comparing the extent of weed control in test flats treated with a thiocarbamate against that occuring in similar flats treated with both the thiocarbamate and the extender. The soil used in these tests was a sandy loam soil from Sunol, Calif., which was pre-treated with the herbicide to simulate a typical field which had received previous herbicide applcations. The Sunol sandy loam soil analyzed as follows: sand 63.1%; silt-21.2%; clay-12.4%, organic matter-1%; and pH 6.9. cl A. Soil Pre-Treatment

A solution was prepared by diluting an emulsifiable liquid concentrate containing 6 lb/gal (0.72 kg/l) (76.8% by weight) of the herbicide S-ethyl di-n-propylthiocarbamate in 200 ml of water, such that the resulting concentration of herbicide in the solution was 2000 mg/l. Two hundred ml of this solution was then added to 200 lb (90.8 kg) of soil to which 17-17-17 fertilizer had been previously added to a concentration of 50 ppm by weight with respect to the soil. The mixture was mixed in a rotary mixer for 10 to 30 minutes.

The soil was then placed in round plastic containers, 7.5 inches (19.0 cm) in diameter by 7.5 inches (19.0 cm) deep. The soil was tamped and leveled with a row marker to impress one row across the width of each container. This row was seeded with watergrass (Echinochloa crus-galli). Sufficient seeds were planted to produce several seedlings. The containers were then placed in a greenhouse maintained at 20° C. to 30° C. and watered daily by sprinkler.

Five weeks after treatment, the soil was allowed to dry out and the plant foliage was removed. The soil was then passed through a 0.25 inch (0.64 cm) screen to remove plant roots and clods.

B. Herbicide Test

A solution was prepared by diluting an emulsifiable liquid concentrate containing 6 lb/gal. (0.72 kg/l) (76.8% by weight) of the herbicide S-ethyl N,N-di-n-propylthiocarbamate in 675 ml of water such that the resulting concentration of herbicide in the solution was 1.48 mg/ml. Five ml of this solution when added to three pounds of soil yielded a quantity in the soil equivalent to three pounds per acre.

The extender compounds were used in technical form. These materials were added 5 ml acetone and 14.5 ml water such that the resulting concentration of the extender in the solution was 1.54 mg/ml. Five ml of this solution when added to three pounds of soil yielded a quantity in the soil equivalent to four pounds per acre.

Five ml of the extender solution and 5 ml of the herbicide solution were tank-mixed. The resultant mixture of 10 ml was then added to 3 lbs of soil and incorporated into the soil by a rotary mixer. Thus, 10 ml of the mixture and 3 pounds of soil were placed in rotary mixter and incorporated.

The treated soil was then placed in aluminum flats which were approximately 3 inches deep, 4 inches wide, and 8 inches long (7.6×10.2×20.3 cm). The soil was tamped and leveled with a row marker to impress six rows across the width of the flat. The test weeds were as follows:

    ______________________________________                                                     ABBRE-                                                             COMMON NAME VIATION    SCIENTIFIC NAME                                         ______________________________________                                         watergrass  WG         Echinochloa crus-galli (L.)                             wild oats   WO         Avena fatua (L.)                                        wild cane   WC         Sorghum bicolor (L.) Moench                             ______________________________________                                    

R-10 milo (Sorghum bicolor) was also used as a plant growth indicator. Two rows of watergrass were planted.

One row of DeKalb XL-25A corn of species Zea mays (L.) was planted.

Sufficient seeds were planted to produce several seedlings per inch in each row. The flats were then placed in a greenhouse maintained at 70° to 85° F. (21° to 30° C.) and watered daily by sprinkler.

Approximately three weeks after treatment, the degree of weed control and corn injury were estimated and recorded as a percentage compared to the growth of the same species in a check flat of the same age which had been seeded in conditioned soil but not treated with either an herbicide or an extender. The rating scale ranges from 0 to 100%, where 0 equals no effect with plant growth equal to the untreated check, and 100 equals complete kill.

The results are listed in Table 1. The average percentage of weed control in the last column is the average for the above-identified weed species and plant growth indicator. There was no injury to the corn in any of the tests. Control experiments (herbicide alone with no extender present) were included in each batch for comparison. Substantial improvements in average percent weed control over the control experiments are evident. The herbicidal efficay of the thiocarbamate three weeks after application was much improved by the use of the extender, whereas the corn remained unaffected.

An asterisk (*) indicates the percentage is an average of two trials.

                                      TABLE 1                                      __________________________________________________________________________     Herbicidal Activity                                                                      Herbicide: S-ethyl N,N-di-n-propyl thiocarbamate                               Application Rate: Herbicide 3 lb/A - Extender 4 lb/A                           Herbicide Alone: 10% Average Weed Control                                      Rating Time: Two weeks after treatment.                              Cmpd.                                                                              Extender                          Ave. %                                   No. R.sup.4Y    R.sup.3                                                                              XR.sup.6        Weed Control                             __________________________________________________________________________     1   C.sub.2 H.sub.5 O                                                                          C.sub.2 H.sub.5 O                                                                     ##STR6##       38%                                      2   C.sub.2 H.sub.5 O                                                                          C.sub.2 H.sub.5                                                                       ##STR7##       40%                                      3   CH.sub.3 CHCHCH.sub.2 O                                                                    C.sub.2 H.sub.5                                                                       ##STR8##       38%                                      4   C.sub.2 H.sub.5 O                                                                          C.sub.2 H.sub.5 O                                                                     ##STR9##       34%                                      5   (CH.sub.3).sub.2 CHCH.sub.2 CH.sub.2 O                                                     C.sub.2 H.sub.5                                                                       ##STR10##      47%                                      6   C.sub.2 H.sub.5 O                                                                          C.sub.2 H.sub.5 O                                                                     ##STR11##      34%                                      7   CH.sub.2CHCH.sub.2 O                                                                       C.sub.2 H.sub.5                                                                       ##STR12##      34%                                      8   n-C.sub.4 H.sub.9 S                                                                        C.sub.2 H.sub.5                                                                      SCH.sub.2 SCH.sub.2 CH.sub.3                                                                   35%                                      9   CH.sub.3 O  CH.sub.3 O                                                                            ##STR13##      37%                                      10  C.sub.2 H.sub.5 O                                                                          C.sub.2 H.sub.5 O                                                                     ##STR14##       85%*                                    11  CH.sub.3 O  CH.sub.3 O                                                                            ##STR15##      55%                                      12  C.sub.3 H.sub.7 O                                                                          C.sub.3 H.sub.7 O                                                                     ##STR16##      69%                                      13  C.sub.2 H.sub.5 O                                                                          C.sub.2 H.sub.5 O                                                                     ##STR17##      96%                                      14  C.sub.2 H.sub.5 O                                                                          C.sub.2 H.sub.5 O                                                                     ##STR18##      70%                                      15  C.sub.2 H.sub.5 O                                                                          C.sub.2 H.sub.5 O                                                                     ##STR19##      42%                                      16  C.sub.2 H.sub.5 O                                                                          C.sub.2 H.sub.5 O                                                                     ##STR20##      76%                                      17  C.sub.2 H.sub.5 O                                                                          CH.sub.3 O                                                                            ##STR21##      39%                                      18  n-C.sub.4 H.sub.9 O                                                                        CH.sub.3 O                                                                            ##STR22##      65%                                      19  ClC.sub.2 H.sub.4 O                                                                        C.sub.2 H.sub.5 O                                                                     ##STR23##      55%                                      20  C.sub.2 H.sub.5 O                                                                          C.sub.2 H.sub.5 S                                                                     ##STR24##      92%                                      21  C.sub.2 H.sub.5 O                                                                          n-C.sub.3 H.sub.7 S                                                                   ##STR25##      96%                                      22  C.sub.2 H.sub.5 O                                                                          i-C.sub.3 H.sub.7 S                                                                   ##STR26##      45%                                      23  CH.sub.3 (CH.sub.2).sub. 3 S                                                               C.sub.2 H.sub.5 O                                                                     ##STR27##      90%                                      24  sec-C.sub.4 H.sub.9 S                                                                      C.sub.2 H.sub.5 O                                                                     ##STR28##      34%                                      25  i-C.sub.4 H.sub.9 S                                                                        C.sub.2 H.sub.5 O                                                                     ##STR29##      57%                                      26  n-C.sub.3 H.sub.7 O                                                                        C.sub.2 H.sub.5 S                                                                     ##STR30##      68%                                      27  n-C.sub.3 H.sub.7 O                                                                        n-C.sub.3 H.sub.7 S                                                                   ##STR31##      64%                                      28  i-C.sub.3 H.sub.7 S                                                                        n-C.sub.3 H.sub.7 O                                                                   ##STR32##      37%                                      __________________________________________________________________________

The last two provisos in the first preferred embodiment, supra, were designed to delete organophosphorus compounds which were tested according to the procedures of this example but did not show significant extending activity.

The compounds referred to by said provisos are those listed below in Table A.

                  TABLE A                                                          ______________________________________                                         R.sup.4Y         R.sup.5   XR.sup.6                                            ______________________________________                                         Proviso 2                                                                             CH.sub.2CHCH.sub.2 O                                                                         CH.sub.3                                                                                  ##STR33##                                      Proviso 3                                                                             CH.sub.3 S    CH.sub.3 S                                                                                ##STR34##                                             CH.sub.3 S    C.sub.2 H.sub.5 O                                                                         ##STR35##                                             CH.sub.3 O    C.sub.2 H.sub.5 S                                                                         ##STR36##                                             CH.sub.3 O    n-C.sub.3 H.sub.7 S                                                                       ##STR37##                                             CH.sub.3 O    i-C.sub.3 H.sub.7 S                                                                       ##STR38##                                             CH.sub.3 O    n-C.sub.4 H.sub.9 S                                                                       ##STR39##                                      ______________________________________                                    

The following Examples 2-13 demonstrate the effectiveness of the organophosphorus extenders of this invention in slowing the rate of degradation of thiocarbamates herbicides (Examples 2,4) and of extending the soil life of thiocarbamates by bioassay results as in Example 1, above (Examples 3, 5, 6, 7, 8, 9, 10, 11, 12, and 13).

Example 3 shows the activity of a variety of organophosphorus compounds with S-ethyl N,N-di-n-propyl thiocarbamate with and without an antidote in a number of different types of soils that has a prior history of thiocarbamate herbicide treatment.

Example 4 presents chemical analyses indicating as does Example 2 the slowed degradation of thiocarbamate herbicides in the presence of an organophosphorus compound of this invention. In Example 4, however, the soil was pre-treated with a thiocarbamate herbicide in the greenhouse.

Examples 5-7, 9 and 11-13 show bioassay results indicating the effectiveness of representative extenders in extending the soil life of a variety of thiocarbamate herbicides in compositions with and without a variety of antidotes.

Example 8 shows a thiocarbamate herbicide, an antidote and an extender tested alone and in combination in soil which had not been pretreated with a thiocarbamate herbicide.

Example 10 was designed to show that a representative extender when tested alone in soil pre-treated with a thiocarbamate herbicide has no herbicidal activity.

EXAMPLE 2 Soil Persistence Tests

This example shows, by periodic chemical analyses of soil composition, the effectiveness of the organophosphorus compounds of the present invention in slowing down the rate of degradation of the thiocarbamate herbicide.

A one-pint (0.5 liter) glass canning jar containing 250 grams (g) of soil (on an air-dry basis) was used for each test. Soils of three different textures were used: a loamy sand from Sunol, Calif.; a silty loam from Thurman, Iowa; and a loam from Tracy, Calif. All of these soils had a prior history of thiocarbamate herbicide treatment. The relative amounts of sand, silt, and clay of each soil type were determined by mechanical means, and the quantity of organic matter and the acidity (pH) were determined chemically. The results of these analyses are shown below:

    ______________________________________                                         Soil Analyses                                                                         Composition (Weight %)                                                                         Organic Matter                                          Source   Sand    Silt     Clay   (Weight %)                                                                               pH                                  ______________________________________                                         Sunol, CA                                                                               64      29        7     4         6.8                                 Thurman, IA                                                                             32      56       12     3         7.2                                 Tracy, CA                                                                               50      30       20     4.7       6.1                                 ______________________________________                                    

The test compounds or combinations were dissolved in water at concentrations calculated such that a 5.0 cubic centimeter (cc) aliquot contained quantities of active ingrediens equivalent to the desired application rates when added to the jar. The thiocarbamates used in these tests were applied in the form of emulsifiable liquid concentrates containing an antidote to prevent crop injury. The concentrates were appropriately diluted to correspond to an application rate of 6.0 lb/A (6.72 kilograms/hectare) of active ingredient. Of the organophosphorus compounds tested, O,O-diethyl-O-phenyl phosphorothioate was applied as a technical liquid diluted for an application rate of 0.5 lb/A (0.56 kilograms/hectare) or 1.0 lb/A (1.12 kilograms/hectare), and O-ethyl-S-phenyl ethylphosphonodithioate was applied as an emulsifiable liquid concentrate diluted for an application rate of 4.0 lb/A (4.48 kilograms/hectare) of active ingredient.

Thus, a 5.0 cc aliquot of an aqueous mixture, containing the thiocarbamate, the antidote, and the organophosphorus additive in appropriate concentrations, was transferred by pipette to the jar and incorporated into the soil with a spatula. The jar was then sealed with a lid and shaken manually for approximately thirty seconds.

Following such treatment, the soil was seeded with approximately fifty barnyardgrass (Echinochloa crus-galli) seeds and two seeds of DeKalb XL-45A corn. The soil was then moistened to field capacity and the jar was placed unsealed in a greenhouse where the temperature was maintained at approximately 70° to 80° F. (21° to 27° C.) and the soil was moistened periodically.

The tests were performed in duplicate and a separate jar was used for each test. After a specified interval, two jars were removed from the greenhouse, stripped of their foliar plant material, sealed tightly, and frozen to await chemical analysis. After an additional interval, a second pair was removed and similarly treated. In all, six such pairs for each application rate were prepared for analysis, including one pair taken immediately after treatment with the test chemicals for use as a zero time treatment.

Each prepared sample was macerated with 2.0 liters of water in a Waring Blender, then transferred to a 4.0 liter flask. Approximately 10.0 milliliters (ml) of an anti-foaming agent was added. The mixture was distilled rapidly, and approximately 400 ml of distillate was collected. Five drops of concentrated hydrochloric acid were added to the distillate to suppress emulsion formation. The thiocarbamate was extracted from the distillate with two 4.0 ml portions of isooctane. The extracts were then combined for analysis for thiocarbamate content by gas chromatography.

In Tables 2 and 3, the chromatogram data has been converted to equivalent soil concentrations in parts per million (ppm) by weight of thiocarbamate. These tables list the results as averages for each pair of duplicates.

The tables clearly show that the thiocarbamate content declined with time in each type of soil tested. They further show that such decline was substantially lessened by the presence of the organophosphorus compound. The effect of the organophosphorus compound on the Sunol soil is particularly evident from 21 days on in Table 2 and from three weeks on in Table 3, by comparing the experimental entries with control. The higher figures for the experimental entries are a clear indication that the rate of decline is substantially decreased due to the presence of the organophosphorus compound. A similar effect on the Tracy soil is evident from three days on in Table 2 and from one week on in Table 3. Finally, a similar effect is observed in the Thurman soil from seven days on in Table 2 and from two weeks on in Table 3.

                                      TABLE 2                                      __________________________________________________________________________     Soil Persistence Test Results                                                  Herbicide: S-ethyl N,N-di-n-propylthiocarbamate (active ingredient) in         12:1 weight ratio                                                              with N,N-diallyl dichloroacetamide (antidote)                                  Herbicide Application Rate: 6.0 lb/A                                                                      Amount of Herbicide Present in Soil                                     Additive                                                                              (ppm active ingredient).sup.a                                           Application                                                                           Days Following Application                          Organophosphorus Additive                                                                          Rate (lb/A)                                                                           0  3  7  14 21 28                                   __________________________________________________________________________                                Soil used: from Sunol, California                   None (control)      --     11.71                                                                             9.97                                                                              7.88                                                                              6.12                                                                              0.76                                                                              0.71                                 O,O-diethyl-O-phenyl phosphorothioate                                                              0.5    11.43                                                                             10.25                                                                             8.41                                                                              6.88                                                                              5.38                                                                              2.28                                 O,O-diethyl-O-phenyl phosphorothioate                                                              1.0    12.10                                                                             10.23                                                                             10.91                                                                             6.79                                                                              5.74                                                                              3.95                                 O-ethyl-S-phenyl ethylphosphonodithioate                                                           4.0    10.36                                                                             11.70                                                                             8.05                                                                              5.17                                                                              3.18                                                                              1.04                                                            Soil used: from Tracy, California                   None (control)      --     10.59                                                                             2.58                                                                              0.24                                                                              0.12                                                                              0.00                                                                              --.sup.b                             O,O-diethyl-O-phenyl phosphorothioate                                                              0.5    12.05                                                                             9.05                                                                              7.26                                                                              0.82                                                                              0.41                                                                              --                                   O,O-diethyl-O-phenyl phosphorothioate                                                              1.0    12.02                                                                             10.04                                                                             7.58                                                                              1.23                                                                              0.38                                                                              --                                   O-ethyl-S-phenyl ethylphosphonodithioate                                                           4.0    10.24                                                                             9.54                                                                              1.48                                                                              0.30                                                                              0.00                                                                              --                                                              Soil used: from Thurman, Iowa                       None (control)      --     15.79                                                                             8.75                                                                              0.40                                                                              0.27                                                                              0.22                                                                               --                                  O,O-diethyl-O-phenyl phosphorothioate                                                              0.5    12.24                                                                             9.38                                                                              5.87                                                                              0.51                                                                              0.43                                                                              --                                   O,O-diethyl-O-phenyl phosphorothioate                                                              1.0    12.68                                                                             10.88                                                                             9.26                                                                              0.55                                                                              0.39                                                                              --                                   O-ethyl-S-phenyl ethylphosphonodithioate                                                           4.0    11.47                                                                             8.88                                                                              4.29                                                                              0.24                                                                              0.18                                                                              --                                   __________________________________________________________________________      .sup.a Each figure shown represents the average of two samples.                .sup.b Dashes represent samples not analyzed.                            

                                      TABLE 3                                      __________________________________________________________________________     Soil Persistence Test Results                                                  Herbicide: S-ethyl N,N-diisobutylthiocarbamate (active ingredient) in          24:1 weight ratio                                                              with N,N-diallyl dichloroacetamide (antidote)                                  Herbicide Application Rate: 6.0 lb/A                                                                      Amount of Herbicide Present in Soil                                     Additive                                                                              (ppm active ingredient).sup.a                                           Application                                                                           Weeks Following Application                         Organophosphorus Additive                                                                          Rate (lb/A)                                                                           0  1  2  3  4  5                                    __________________________________________________________________________                                Soil used: from Sunol, California                   None (control)      --     9.00                                                                              7.30                                                                               6.15                                                                             3.35                                                                              0.68                                                                              0.30                                 O,O-diethyl-O-phenyl phosphorothioate                                                              1.0    9.40                                                                              7.10                                                                               6.55                                                                             5.25                                                                              5.18                                                                              3.65                                                            Soil used: from Tracy, California                   None (control)      --     8.05                                                                              1.25                                                                               0.13                                                                             0.17                                                                              0.07                                                                              0.03                                 O,O-diethyl-O-phenyl phosphorothioate                                                              1.0    7.95                                                                              7.45                                                                               6.05                                                                             5.65                                                                              4.84                                                                              0.66                                                            Soil used: from Thurman, Iowa                       None (control)      --     8.35                                                                              7.00                                                                               0.16                                                                             0.11                                                                              0.07                                                                              0.07                                 O,O-diethyl-O-phenyl phosphorothioate                                                              1.0    8.35                                                                              7.10                                                                               4.90                                                                             2.11                                                                              1.18                                                                              0.37                                 __________________________________________________________________________      .sup.a Each figure shown represents the average of two samples.          

EXAMPLE 3 Herbicidal Activity Improvement Tests

This example offers herbicidal activity test data to show the effectiveness of the organophosphorus additives in improving the herbicidal activity of thiocarbamates. The effect is observed by comparing the extent of weed control in test flats treated with a thiocarbamate against that occuring in similar flats treated with both the thiocarbamate and an organophosphorus compound.

As in Example 2, the thiocarbamate used in this test was applied in the form of an emulsifiable liquid concentrate containing 6 lb/gal (0.72 kg/l) active ingredient. In several of the tests as indicated, an antidote was included in the formulation to prevent crop injury. The organophosphorus compounds were primarily used in technical form, although emulsifiable liquids, granules, and microcapsules were also used, as indicated.

Stock solutions were prepared by adding appropriate amounts of the formulated test chemicals to 100 cc mixtures containing equal parts of water and acetone. Five cc of a stock solution was then added to three pounds of soil containing approximately 5% mositure in a 5-gallon (18.9 liter) rotary mixer where the soil and stock solution were mixed for 10 to 20 seconds. Such a method of application of the herbicidal compositions is called pre-plant soil incorporation (PPI).

The soil was then placed in aluminum flats which were 2.5 inches (6.4 cm) deep, 3.5 inches (8.9 cm) wide, and 7.5 inches (19.0 cm) long. The soil was tamped and leveled with a row marker to impress six rows across the width of the flat. The seeds of six grass species were planted in the marked rows and covered with soil. The test grass species varied from test to test and including the following:

    ______________________________________                                         COMMON NAME    SCIENTIFIC NAME                                                 ______________________________________                                         yellow foxtail Setaria lutescens (Weigel) Hubb.                                barnyardgrass  Echinochloa crus-galli (L.) Beauv.                              milo           Sorghum bicolor (L.) Moench                                     barley         Hordeum vulgare (L.)                                            giant foxtail  Setaria faberi Herrm                                            wild cane      Sorghum bicolor (L.) Moench                                                    (variant of milo)                                               ______________________________________                                    

Corn was also planted in some of the tests. The corn used was DeKalb XL-45A corn of species Zea mays (L).

Sufficient seeds were planted to produce several seedlings per inch in each row. The flats were then placed in a greenhouse maintained at 70° to 85° F. and watered daily by sprinkler.

Three weeks after treatment, the degree of weed control and corn injury were estimated and recorded as percentage control compared to the growth of the same species in an untreated check flat of the same age. The rating scale ranges from 0 to 100%, where 0 equals no effect with plant growth equal to the untreated control, and 100 equals complete kill.

Tables 4, 5, 6 and 7 which follow list the results of these tests. A control experiment is included in each table for comparison. Substantial improvements in average percent weed control over the control experiment are evident in each table at all application rates of the organophosphorus additive. While all the data in any single table was obtained at the same time under the same conditions, variations exist from one table to the next due to the difficulty in duplicating environmental conditions on different dates. The variations are also due to the fact that different weed combinations and/or soils were used. On the whole, however, it is clear that herbicidal efficacy of the thiocarbamate three weeks after application was much improved by the use of the organophosphorus additive.

                                      TABLE 4                                      __________________________________________________________________________     Herbicidal Activity on Barley, Barnyardgrass, Milo and Giant Foxtail           Herbicide:    S-ethyl N,N-di-n-propylthiocarbamate as 6 lb/gallon                            emulsifiable liquid containing, where shown,                                   N,N-diallyl dichloroacetamide antidote in 12:1 weight                          ratio                                                            Applicaticn Rate:                                                                            3.0 lb/A                                                         Soil Source:  Tracy, California                                                Evaluation Time:                                                                             3 weeks after treatment                                                                Without Antidote                                                                         With Antidote                                                        Average   Average                                                       Application                                                                           % Weed                                                                              % Corn                                                                              % Weed                                                                              % Corn                                    Organophosphorus Additive                                                                     Rate (lb/A)                                                                           Control                                                                             Injury                                                                              Control                                                                             Injury                                    __________________________________________________________________________     None (control).                                                                               --     65   0    58   0                                         O-ethyl-S-phenyl ethyl-                                                                       0.5    92   60   95   0                                         ethylphosphonodithioate                                                                       1.0    100  100  100  20                                        (4 E).sup.a    2.0    100  80   100  0                                                        4.0    100  100  99   0                                         O-ethyl-S-phenyl ethyl-                                                                       0.5    97   90   78   0                                         phosphonodithioate (10 G).sup.b                                                               1.0    100  80   81   0                                                        2.0    100  90   88   0                                                        4.0    100  90   99   10                                        O,O-diethyl-S-ethyl-                                                                          1.0    80   20                                                  thioethylphosphorodi-                                                                         2.0    85   40                                                  thiaote (technical)                                                                           4.0    87   50                                                  O,O-diethyl-O-p-methyl-                                                                       1.0    96   60                                                  sulfinylphenylphosphoro-                                                                      2.0    100  95                                                  dithioate (technical)                                                                         4.0    100  90                                                  O,O-dimethyl-O-p-                                                                             1.0    98   70                                                  nitropheylphosphoro-                                                                          2.0    95   70                                                  thioate (technical)                                                                           4.0    100  90                                                  (technical)                                                                    __________________________________________________________________________      .sup.a 4 E: Emulsifiable liquid containing 4 lb/gal active ingredient.         .sup.b 10 G: Granular formulation containing 10% by weight active              ingredient.                                                              

                                      TABLE 5                                      __________________________________________________________________________     Herbicidal Activity on Yellow Foxtail, Barnyardgrass and Wild Cane             Herbicide:     S--ethyl N,N-di-n-propylthiocarbamate as 6 lb/gal                              emulsifiable liquid                                             Application Rate:                                                                             3.0 lb/A                                                        Evalution Time:                                                                               3 weeks after treatment                                                              Tracy, CA Soil                                                                           Thurman, IA Soil                                                     Average   Average                                                       Application                                                                           % Weed                                                                              % Corn                                                                              % Weed                                                                              % Corn                                     Organophosphorus Additive                                                                    Rate (lb/A)                                                                           Control                                                                             Injury                                                                              Control                                                                             Injury                                     __________________________________________________________________________     None (control)                                                                               --      4   0    14   0                                          O,O-dimethyl-O-phenylphos-                                                                   0.5    18   0    16   0                                          phorothioate (technical)                                                                     1.0    26   0    34   0                                                        2.0    30   0    44   0                                          O,O-diethyl-O-phenyl-                                                                        0.5    48   0    38   0                                          phosphorothioate                                                                             1.0    81   0    76   0                                          (technical)                                                                    O,O-diisopropyl-O-phenyl-                                                                    0.5    40   0    30   0                                          phosphorothioate                                                                             1.0    42   0    46   0                                          (technical)   2.0    56   0    58   0                                          O,O-di-n-propyl-O-phenyl-                                                                    0.5    30   0    44   0                                          phosphorothioate                                                                             1.0    50   0    50   0                                          (technical)   2.0    86   0    81   0                                          O,O-dimethyl-O-benzyl-                                                                       1.0    32   0    32   0                                          phosphorothioate                                                                             2.0    54   0    38   0                                          (technical)                                                                    O,O-diethyl-O-(2-phenyl-                                                                     1.0    32   0    32   0                                          ethyl)phosphorothioate                                                                       2.0    46   0    32   0                                          (technical)                                                                    __________________________________________________________________________

                  TABLE 6                                                          ______________________________________                                         Herbicidal Activity on Yellow Foxtail, Barnyardgrass,                          Milo and Wild Cane                                                             Herbicide: S-ethyl N,N-di-n-propylthiocarbamate as 6 lb/gal                               emulsifiable liquid                                                 Application Rate:                                                                         3.0 lb/A                                                            Evalution Time:                                                                           3 weeks after treatment                                             Soil Source:                                                                              Tracy, CA                                                           ______________________________________                                                       Average % Weed Control                                                         Application Rates (lb/A) at:                                     Organophosphorus Additive                                                                      0      0.125  0.25 0.50 1.0  2.0                               ______________________________________                                         (control)                                                                      O-ethyl-S-phenyl ethyl-                                                        phosphonodithioate                                                                             20     --     49   72   90   93                                (technical)                                                                    O,O-diethyl-O-phenyl-                                                          phosphorothioate                                                                               20     88     91   94   96   --                                (technical)                                                                    O,O-diethyl-O-phenyl                                                           phosphorothioate                                                                               20     89     93   94   95   --                                (microcapsule)                                                                 O,O-dimethyl-O-phenyl-                                                         phosphorothioate                                                                               20     32     54   72   87   --                                (technical)                                                                    ______________________________________                                    

                  TABLE 7                                                          ______________________________________                                         Herbicidal Activity on Yellow Foxtail, Barnyardgrass,                          Milo and Wild Cane                                                             Herbicide:   S-ethyl N,N-di-propylthiocarbamate as                                          6 lb/gal emulsifiable liquid                                      Application Rate:                                                                           3.0 lb/A                                                          Evaluation Time:                                                                            3 weeks after treatment                                           Soil Source: Thurman, Iowa                                                     ______________________________________                                                         Average % Weed Control                                                        Application Rates (lb/A) at:                                    Organophosphorus Additive                                                                       0        0.50   1.0  2.0 4.0                                  ______________________________________                                         (control)                                                                      O,O-diethyl-O-phenyl phos-                                                                      22       60     62   82  92                                   phorothioate (technical)                                                       O-ethyl-S-phenyl ethylphos-                                                                     42       8      16   24  28                                   phonodithioate (technical)                                                     O,O-diethyl-O-(2-phenylethyl)                                                                   22       14     20   46  64                                   phosphorothioate (technical)                                                   O--O-di-n-propyl-O-phenyl                                                                       22       38     50   70  84                                   phosphorothioate (technical)                                                   O-ethyl-S-ethyl-O-phenyl                                                                        22       36     56   76  90                                   phosphorothioate (technical)                                                   ______________________________________                                    

EXAMPLE 4 Accelerated Soil Persistence Tests

The tests shown in this example are similar to those of Example 2, except that the soil was pre-treated in the greenhouse to magnify and accelerate its effect in causing the herbicide content to decline. The soil from Sunol, Calif., described in Example 2 was used in all tests.

A. Soil Pre-Treatment

A solution was prepared by diluting an emulsifiable liquid concentrate containing 6 lb/gal (0.72 kg/l) of the herbicide S-ethyl N,N-di-n-propylthiocarbamate in 100 ml of water, such that the resulting concentration of herbicide in the solution was 4000 mg/l. Five ml of this solution was then added to 10 lb (4.54 kg) of soil and the mixture was mixed in a rotary mixer for 10-20 seconds.

The soil was then placed in round plastic containers, 9 inches (22.9 cm) in a diameter by 9 inches (22.9 cm) deep. The soil was tamped and leveled with a row marker to impress three rows across the width of each container. Two rows were seeded with DeKalb XL-45A corn (Zea mays), and one row was seeded with barnyardgrass (Echinochloa crus-galli). Sufficient seeds were planted to produce several seedlings per row. The containers were then placed in a greenhouse maintained at 20° C. to 30° C. and watered daily by sprinkler.

Five weeks after treatment, the soil was allowed to dry out and the plant foliage was removed. The soil was then passed through a 0.25 inch (0.64 cm) screen to remove plant roots and clods, and then passed through a 2 millimeter (mm) screen.

B. Soil Persistence Test

A 100-gram quantity (air-dry basis) of the pre-treated soil was placed in an 8 ounce (0.24 liter) wide-mouth glass bottle. The same emulsifiable concentrate described in Part A above was appropriately diluted in water such that a 5 ml portion added to the soil would produce a herbicide concentration of 6 ppm (weight) in the soil. A selected extender compound in technical (nonformulated) form was then diluted in an acetone-water mixture such that a one ml portion added to the soil would produce a concentration of 4 ppm (weight). On these bases, the herbicide and extender were added to the bottle containing the soil. The bottle was then sealed with a lid and shaken manually for approximately 15 minutes. The bottle of soil was placed in an environmental growth chamber where the temperature was maintained at approximately 25° C.

Two days later, the bottle was removed from the environmental chamber and 50 ml of water and 100 ml of toluene were added. The bottle was then tightly sealed with a lid containing a cellophane liner, and vigorously shaken on a variable speed, reciprocating shaker (Eberback Corp. Model No. 6000) set approximately 200 excursions per minute for one hour. After shaking, the bottle contents were allowed to settle, and a 10 ml aliquot of toluene was transferred by pipette into a glass vial and sealed with a polyseal cap. The toluene extract was analyzed for herbicide content by gas chromatography. The chromatogram data was then converted to equivalent soil concentrations in parts per million (ppm) by weight of the herbicide.

The results are shown in Tables 8, 9 and 10, which represent three separate pre-treatment batches. Two control runs are included in each table (where the herbicide was applied alone). In each case, substantially more herbicide remains in the soil when an extender compound is present.

                                      TABLE 8                                      __________________________________________________________________________     2-Day Soil Persistence Tests - Run #1                                          Herbicide:    S-ethyl N,N-di-n-propylthiocarbamate                             Application Rate:                                                                            Herbicide 6 ppm (weight)                                                       Extender 4 ppm (weight)                                          Herbicide Alone:                                                                             Trial A: 0.22                                                                             Residue After 2 Days (ppm)                                          Trial B: 0.23                                                    Herbicide with Extender:                                                                      ##STR40##                                                                                       Herbicide                                                                      Residue                                        Cmpd.                                                                              Extender                    After                                          No. R.sup.4Y                                                                             R.sup.5                                                                             XR.sup.6         2 Days (ppm)                                   __________________________________________________________________________     1   C.sub.2 H.sub.5 O                                                                   C.sub.2 H.sub.5 O                                                                     ##STR41##       3.97                                           __________________________________________________________________________

                                      TABLE 9                                      __________________________________________________________________________     2-Day Soil Persistence Tests - Run #2                                          Herbicide:    S-ethyl N,N-di-n-propylthiocarbamate                             Application Rate:                                                                            Herbicide 6 ppm (weight)                                                       Extender 4 ppm (weight)                                          Herbicide Alone:                                                                             Trial A: 1.42                                                                             Residue After 2 Days (ppm)                                          Trial B: 1.23                                                    Herbicide with Extender:                                                                      ##STR42##                                                                                        Herbicide                                                                      Residue                                       Cmpd.                                                                              Extender                     After                                         No. R.sup.4Y   R.sup.5                                                                             XR.sup.6     2 Days (ppm)                                  __________________________________________________________________________     2   C.sub.2 H.sub.5 O                                                                         C.sub.2 H.sub.5                                                                      ##STR43##   2.26                                          3   CH.sub.3 CHCHCH.sub.2 O                                                                   C.sub.2 H.sub.5                                                                      ##STR44##   2.88                                          __________________________________________________________________________

                                      TABLE 10                                     __________________________________________________________________________     2-Day Soil Persistence Tests - Run # 3                                         Herbicide:    S-ethyl N,N-di-n-propylthiocarbamate                             Application Rate:                                                                            Herbicide 6 ppm (weight)                                                       Extender 4 ppm (weight)                                          Herbicide Alone:                                                                             Trial A: 0.13                                                                             Residue After 2 Days (ppm)                                          Trial B: 0.11                                                    Herbicide with Extender:                                                                      ##STR45##                                                                                          Herbicide                                                                      Residue                                     Cmpd.                                                                              Extender                       After                                       No. R.sup.4Y    R.sup.5                                                                             XR.sup.6      2 Days (ppm)                                __________________________________________________________________________     4   C.sub.2 H.sub.5 O                                                                          C.sub.2 H.sub.5 O                                                                    ##STR46##    1.08                                        5   (CH.sub.3).sub.2 CHCH.sub.2 CH.sub.2 O                                                     C.sub.2 H.sub.5                                                                      ##STR47##    0.92                                        __________________________________________________________________________

EXAMPLE 5 Herbicidal Activity Improvement Tests

The tests described in this example are similar to those of Example 3, except that 2,2,5-trimethyl-N-dichloromethyl oxazolidine was used as the antidote rather than N,N-diallyl dichloroacetamide, and the soil was pre-treated in a manner similar to that described in Example 4 to simulate a field with a history of prior treatment with the same herbicide. The herbicide was S-ethyl di-n-propylthiocarbamate, the extender compound was O,O-diethyl-O-phenyl phosphorothioate, and the soil was a sandy loam soil from San Jose, Calif.

A. Soil Pre-Treatment

The procedure of Example 4, section A, was used, with a treating solution containing b 2000 mg/l of herbicide rather than 4000.

B. Herbicide Test

The pre-plant soil incorporation procedure of Example 3 was followed, using aluminum planting flats measuring 4 inches (10.2 cm) deep, 6 inches (15.2 cm) wide, and 9 inches (22.9 cm) long, and the following weed species:

    ______________________________________                                         COMMON NAME    SCIENTIFIC NAME                                                 ______________________________________                                         watergrass     Echinochloa crus-galli (L.) Beauv.                              wild oats      Avena fatua (L.)                                                wild cane      Sorghum bicolor (L). Moench                                     annual ryegrass                                                                               Lolium multiflorum (Lam.)                                       milo           Sorghum bicolor (L.) Moench                                     yellow foxtail Setaria lutescens (Weigle) Hubb.                                ______________________________________                                    

The results are shown in Table 11, clearly indicating a marked improvement in the herbicidal efficacy of the herbicide/antidote combination three weeks after application, by the inclusion of the extender compound.

                                      TABLE 11                                     __________________________________________________________________________     Herbicidal Activity                                                            Herbicide:                                                                             S-Ethyl di-n-propylthiocarbamate                                       Antidote:                                                                              2,2,5-Trimethyl-N-dichloroacetyl oxazolidine                           Extender:                                                                              O,O-Diethyl-O-phenyl phosphorothioate                                  __________________________________________________________________________                     Percent Control After 3 Weeks                                  Application Rates (lb/A                                                                        Water-                                                                             Wild                                                                              Wild                                                                              Rye    Fox-                                          Herbicide                                                                            Antidote                                                                            Extender                                                                            grass                                                                              oats                                                                              cane                                                                              grass                                                                              Milo                                                                              tail                                          __________________________________________________________________________     3.0   0.125                                                                               --   0   10 15 85  20 0                                             3.0   0.125                                                                               0.5  20  45 30 85  30 5                                             6.0   0.25 --   40  55 5  100 15 10                                            6.0   0.25 1.0  75  80 75 100 70 25                                            12.0  0.5  --   70  80 35 95  45 30                                            12.0  0.5  2.0  85  95 90 100 90 70                                            __________________________________________________________________________

EXAMPLE 6 Further Herbicidal Activity Improvement Tests

The tests outlined in this example are carried out in essentially the same manner as in Example 5. As in Example 5, the soil was pre-treated (1st treatment), to simulate a field with a history of prior treatment with the same herbicides, and then retreated (2nd treatment) with the herbicidal test compositions comprising the herbicide and extender, or the herbicide, extender and antidote, as described in Example 3. The tests are different in that:

(1) the herbicides tested were S-ethyl diisobutyl thiocarbamate and S-propyl N,N-dipropyl thiocarbamate;

(2) the antidote, when employed, was N,N-diallyl dichloroacetamide;

(3) the unantidoted tests with S-ethyl diisobutyl thiocarbamate were carried out in river sand;

(4) when stock solutions were prepared both for soil pre-treatment and retreatment, the appropriate amounts of the formulated test chemicals were added to a mixture of 95 cc of water, 5 cc acetone and two drops of the emulsifier polyoxyethylene (20) sorbitan monolaurate, rather than to 100 cc of water;

(5) pre-treatment in the antidoted treatment series was with S-ethyl diisobutyl thiocarbamate plus N,N-diallyl dichloroacetamide;

(6) some flats were untreated at the time of the first treatment to observe weed control under the same conditions in pre-treated and non-pre-treated cases; and

(7) the six grass species tested were the following (five weed species and milo):

    ______________________________________                                         COMMON NAME    SCIENTIFIC NAME                                                 ______________________________________                                         watergrass     Echinochloa crusgalli (L.) Beauv.                               green foxtail  Setaria viridis (L.) Beauv.                                     wild cane      Sorghum bicolor (L.) Moench                                     Johnsongrass   Sorghum halepense (L.) Pers.                                    wild oats      Avena fatua (L.)                                                milo           Sorghum bicolor (L.) Moench                                     ______________________________________                                    

The results as shown in Tables 12, 13, and 14 clearly show that O,O-diethyl-O-phenyl phosphorothioate increased the herbicidal activity of both S-ethyl diisobutylthiocarbamate, antidoted or not, and S-propyl N,N-dipropylthiocarbamate.

                  TABLE 12                                                         ______________________________________                                         HERBICIDAL ACTIVITY                                                            ______________________________________                                         Herbicide    S-ethyl N,N-diisobutyl thiocarbamate                              Extender     O,O-diethyl-O-phenylphosphorothioate                              Rating       22 days after 2nd treatment                                       Weeks Between                                                                               4                                                                 Treatments                                                                     ______________________________________                                         Application Rates: lb/A                                                                               Average %                                               1st Treatment                                                                           2nd Treatment     Control of 6                                        Herbicide                                                                               Herbicide    Extender Grasses Tested                                  ______________________________________                                         0        0            0        0%                                              0        3            0        99.7%                                           3        3            0        69.5%                                           3        3            0.5      99.7%                                           3        3            1        100.0%                                          ______________________________________                                    

                                      TABLE 13                                     __________________________________________________________________________     HERBICIDAL ACTIVITY                                                            __________________________________________________________________________     Herbicide:       S-ethyl N,N-diisobutyl thiocarbamate                          Antidote:        N,N-diallyl dichloroacetamide                                 Extender:        O,O diethyl-O-phenyl phosphorothioate                         Rating:          14 days after 2nd treatent                                    Weeks Between Treatments:                                                                       6                                                             __________________________________________________________________________     Application Rates lb/A                                                         1st Treatment                                                                             2nd Treatment   Average % Control                                   Herbicide                                                                            Antidote                                                                            Herbicide                                                                            Antidote                                                                            Extender                                                                            of 6 Grass Species                                  __________________________________________________________________________     0     0    0     0    0    0                                                   0     0    3     0.167                                                                               0    82.3                                                3     0.167                                                                               3     0.167                                                                               0    16                                                  3     0.167                                                                               3     0.167                                                                               1    87.5                                                __________________________________________________________________________

                                      TABLE 14                                     __________________________________________________________________________     HERBICIDAL ACTIVITY                                                            __________________________________________________________________________     Herbicide:    S-propyl N,N-dipropyl thiocarbamate                              Antidote:     N,N-diallyl dichloroacetamide                                    Extender:     O,O-diethyl-O-phenyl phosphorothioate                            Rating:       14 days after 2nd treatment                                      __________________________________________________________________________     Application Rates lb/A                                                         1st Treatment                                                                             2nd Treatment   Average % Control                                   Herbicide                                                                            Antidote                                                                            Herbicide                                                                            Antidote                                                                            Extender                                                                            of 6 Grass Species                                  __________________________________________________________________________     0     0    0     0    0    0                                                   0     0    3     0.25 0    79.3                                                3     0.25 3     0.25 0    8.3                                                 3     0.25 3     0.25 1    78.8                                                __________________________________________________________________________

EXAMPLE 7 Further Herbicidal Activity Improvement Tests

This example again shows herbicidal activity test data indicating the effectiveness of the extender compounds in improving the herbicidal activity of thiocarbamates. The effect is observed by comparing the extent of weed control in test flats treataed with a thiocarbamate against that occurring in similar flats treated with both the thiocarbamate and the extender. The soil used in these tests was a sandy loam soil from San Jose, Calif., which was pre-treated with the herbicide to simulate a typical field which had received previous herbicide applications.

A. Soil Pre-Treatment

A solution was prepared by diluting an emulsifiable liquid concentrate containing either 6 lb/gal (0.72 kg/l) (75% by weight) of the herbicide S-ethyl N,N-diisobutyl thiocarbamate in 200 ml of water, such that the resulting concentration of herbicide in the solution was 2000 mg/l. Two hundred ml of this solution was then added to 200 lb (90.8 kg) of soil and the mixture was mixed in a rotary mixer for thirty minutes. Also added was 17-17-17 fertilizer (N-P₂ O₅ -K₂ O on a weight basis), amounting to 50 ppm by weight with respect to the soil.

The soil was then placed in round plastic containers, 7.5 inches (19.0 cm) in diameter by 7.5 inches (19.0 cm) deep. The soil was tamped and leveled with a row marker to impress three rows across the width of each container. One row was seeded with DeKalb XL-45A corn (Zea mays), and two rows were seeded with barnyardgrass (Echinochloa crus-galli). Sufficient seeds were planted to produce several seedlings per row. The containers were then placed in a greenhouse maintained at 20° C. to 30° C. and watered daily by sprinkler.

Five weeks after treatment, the soil was allowed to dry out and the plant foliage was removed. The soil was then passed through a 0.25 inch (0.64 cm) screen to remove plant roots and clods, and then passed through a 2 millimeter (mm) screen.

B. Herbicide Test

A thiocarbamate preparation described in Part A was used. The extender compounds were used in technical form. These materials were added to 100 cc mixtures of equal parts of water and acetone at such amounts that 5 cc of the resulting mixture when added to three pounds of soil yielded a quantity in the soil equivalent to the desired application rate expressed in pounds per acre. Thus, 5 cc of the mixture and three pounds of soil were placed in a rotary mixer.

The treated soil was then placed in aluminum flats which were 3 inches deep, 4 inches wide, and 8 inches long (7.6×10.2×20.3 cm). The soil was tamped and leveled with a row marker to impress six rows across the width of the flat. The test weeds were as follows:

    ______________________________________                                         COMMON NAME    SCIENTIFIC NAME                                                 ______________________________________                                         watergrass     Echinochloa crus-galli (L.)                                     milo           Sorghum bicolor (L.) Moench                                     wild oats      Avena fatua (L.)                                                wild cane      Sorghum bicolor (L.) Moench                                     yellow foxtail Setaria lutescens (Weigle) Hubb.                                ______________________________________                                    

DeKalk XL-45A corn of species Zea mays (L.) was also planted.

Sufficient seeds were planted to produce several seedlings per inch in each row. The flats were then placed in a greenhouse maintained at 70° to 85° F. (21° to 30° C.) and watered daily by sprinkler.

Approximately three weeks after treatment, the degree of weed control and corn injury were estimated and recorded as percentage control compared to the growth of the same species in an untreated check flat of the same age. The rating scale ranges from 0 to 100%, where 0 equals no effect with plant growth equal to the untreated control, and 100 equals complete kill.

The results are listed in Tables 15 and 16 each representing a separate batch of tests. Control experiments (with no extender present) were included in each batch for comparison. Substantial improvements in average percent weed control over the control experiments are evident. The herbicidal efficacy of the thiocarbamate three weeks after application was much improved by the use of the extender, whereas the corn remained unaffected.

                                      TABLE 15                                     __________________________________________________________________________     HERBICIDAL ACTIVY TEST                                                         __________________________________________________________________________     Herbicide:      S-ethyl N,N-diisobutyl thiocarbamate at 3 lb/A                 Soil:           San Jose sandy loam soil pre-treated with S-ethyl                              diisobutyl thiocarbamate at 3 lb/A                             Extender:       As shown, at application rate shown                            Evaluation Time:                                                                               20 days after re-treatment                                     __________________________________________________________________________                                         Average %                                         Application                                                                          Water                                                                              Wild                                                                               Wild                                                                               Yellow     Control of 1st                             Extender                                                                              Rate lb/A                                                                            grass                                                                              cane                                                                               oats                                                                               foxtail                                                                            Milo                                                                               Corn                                                                              5 Grasses                                  __________________________________________________________________________     None   --    35  20  40  3   33  0  26                                         (ave. of 2)                                                                    O,O-diethyl-                                                                          1     90  100 100 65  100 0  91                                         O-phenyl                                                                              2     80  100 100 70  100 0  90                                         phosphoro-                                                                            3     75  100 95  70  95  0  87                                         thioate                                                                        O,O-diethyl-                                                                          1     75  100 100 80  100 0  91                                         O-benzyl                                                                              2     85  100 95  85  100 0  93                                         phosphoro-                                                                            3     75  95  95  50  95  0  82                                         thioate                                                                        O-ethyl-                                                                              1     85  95  100 85  95  0  92                                         S-ethyl-O-                                                                            2     85  95  95  80  100 0  91                                         phenyl phos-                                                                          3     80  95  95  80  100 0  90                                         phorothioate                                                                   __________________________________________________________________________

                                      TABLE 16                                     __________________________________________________________________________     HERBICIDAL ACTIVY TEST                                                         __________________________________________________________________________     Herbicide:      S-ethyl N,N-diisobutyl thiocarbamate at 3 lb/A                 Soil:           San Jose sandy loam soil pre-treated with s-ethyl                              diisobutyl thiocarbamate at 6 lb/A                             Extender:       As shown, at application rate shown                            Evaluation Time:                                                                               21 days after re-treatment                                     __________________________________________________________________________                                         Average %                                         Application                                                                          Water                                                                              Wild                                                                               Wild                                                                               Yellow  45A                                                                               Control of 1st                             Extender                                                                              Rate lb/A                                                                            grass                                                                              cane                                                                               oats                                                                               foxtail                                                                            milo                                                                               corn                                                                              5 Grasses                                  __________________________________________________________________________     None   --    90  90  48  88  75  0  78                                         (ave. of 2)                                                                    O,O-diethyl-                                                                          1     85  100 95  90  100 0  94                                         O-phenyl                                                                              2     85  100 95  90  100 0  94                                         phosphoro-                                                                            3     70  95  100 75  100 0  88                                         thioate                                                                        O,O-diethyl-                                                                          1     85  100 95  90  95  0  93                                         O-benzyl                                                                              2     85  100 95  90  100 0  94                                         phosphoro-                                                                            3     90  100 100 90  100 0  96                                         thioate                                                                        O-ethyl-                                                                              1     90  95  100 95  100 0  96                                         S-ethyl-O-                                                                            2     90  100 100 95  100 0  97                                         phenyl phos-                                                                          3     95  100 100 100 100 0  99                                         phorothioate                                                                   __________________________________________________________________________

EXAMPLE 8 Components of Two- and Three- Component Compositions Tested Alone and in Combinations

The following chemicals, alone and in combination, were pre-plant incorporated in San Jose sandy loam soil which had no previous history of thiocarbamate herbicide treatment according to the method of Example 3 with proviso (4) of Example 6:

(1) S-ethyl N,N-dipropyl thiocarbamate at 3 lb/A;

(2) N,N-diallyl dichloroacetamide at 0.25 lb/A;

(3) O,O-diethyl-O-phenyl phosphorothioate at 2 or 4 lb/A;

(4) S-ethyl N,N-dipropyl thiocarbamate at 3 lb/A+N,N-diallyl dichloroacetamide at 0.25 lb/A; and

(5) S-ethyl N,N-dipropyl thiocarbamate at 3 lb/A+N,N-diallyl dichloroacetamide at 0.25 lb/A+O,O-diethyl-O-phenyl phosphorothioate at 2 and 4 lb/A.

The soil was placed in flats and planted with one row of DeKalb XL-43A corn seeds and with rows of the 6 grass species named above in Example 6.

The flats were placed in the greenhouse at 70°-90° F. and watered as needed. The results taken 17 days after treatment are shown in Table 17. The results indicate that S-ethyl N,N-dipropyl thiocarbamate alone injured corn whereas the antidote N,N-diallyl dichloroacetamide and the extender O,O-diethyl O-phenyl phosphorothioate when tested individually neither injured corn nor had any herbicidal activity. When S-ethyl N,N-dipropyl thiocarbamate and the antidote N,N-diallyl dichloroacetamide were tested in combination, there was no injury to corn. S-ethyl N,N-dipropyl thiocarbamate when tested along gave 98.5% control of the weeds, and this degree of weed control did not change significantly when either N,N-diallyl dichloroacetamide or O,O-diethyl-O-phenyl phosphorothioate were added either alone or in combination.

                  TABLE 17                                                         ______________________________________                                         COMPARATIVE SERIES OF BIOASSAY TESTS WITH                                      COMPONENTS OF COMPOSITIONS, ALONE AND                                          IN COMBINATION                                                                 ______________________________________                                         Herbicide: S-ethyl N,N-dipropyl thiocarbamate                                  Antidote:  N,N-diallyl dichloroacetamide                                       Extender:  O,O-diethyl-O-phenyl phosphorothioate                               Rating:    17 days after treatment                                             ______________________________________                                                           % Corn                                                       Application Rates lb/A                                                                           Twisting Average % Control                                   Herbicide                                                                              Antidote Extender Injury of 6 Grass Species                            ______________________________________                                         0       0        0        0      0                                             3       0        0        30     98.5                                          0       0.25     0        0      0                                             0       0        2        0      0                                             0       0        4        0      0                                             3       0.25     0        0      95.5                                          3       0        2        35     98.5                                          3       0.25     2        0      98.2                                          3       0.25     4        0      98.0                                          ______________________________________                                    

EXAMPLE 9 Further Herbicidal Activity Improvement Tests with Three-Component Compositions

Further tests were carried out to show that a representative extender of the instant invention acts to extend the soil life of herbicidal compositions containing a representative thiocarbamate and representative antidotes.

The soil for most flats was pre-treated (1st treatment) and then retreated (2nd treatment) as in Examples 5, 6, 7 and 8. The soild for one flat, however, was not pretreated and was treated with thiocarbamate for the first time at the time the other flats were being retreated. All the flats except that one flat, upon second treatment, were treated with test compositions comprising a thiocarbamate herbicide, a thiocarbamate and extender, a thiocarbamate and an antidote, or a thiocarbamate, antidote and an extender, essentially as described in Example 3. The second treatment differed from the described in Example 3 in that:

1. the aluminum flats were 3 inches (7.6 cm) deep, 6 inches (15.24 cm) wide, and 8 inches (20.32 cm) long;

2. the antidote stock solutions were prepared by dissolving 37 mg of each antidote (technical grade) in 5 ml of acetone and then adding 0.1 ml of a blend of polyoxyethylene ethers of sorbitan monolaurate as an emulsifier and 95 ml of water;

3. 10 ml of the thiocarbamate stock solution was mixed with 10 ml of the antidote stock solution and, in some cases, with 10 ml of the extender stock solution;

4. one row each of the following grass species were planted:

    ______________________________________                                         Commn Name        Scientific Name                                              ______________________________________                                         green foxtail     Setaria viridis                                              watergrass        Echinochloa crus-galli                                       wild cane         Sorghum bicolor;                                             ______________________________________                                    

and

5. also planted in each flat three rows were planted with DeKalb Xl-64 corn of species Zea mays (L.)

The flats were placed in the greenhouse at 70°-90° F. and watered lightly as needed.

The flats were rated 3 weeks after the second treatment. Table 18 indicates the antidotes tested. There was no indication of any herbicidal injury to any of the rows of corn in any flat, so those results are not recorded below in Table 19. The tabulated results indicate that the extender restored the herbicidal activity of the thiocarbamate alone or thiocarbamate and antiodote compositions in soil which had been pretreated with the herbicide.

                  TABLE 18                                                         ______________________________________                                         Antidotes Tested                                                               Antidote                                                                       Compound No.   Structure                                                       ______________________________________                                                         ##STR48##                                                      2                                                                                              ##STR49##                                                      3                                                                                              ##STR50##                                                      4                                                                                              ##STR51##                                                      5                                                                                              ##STR52##                                                      ______________________________________                                    

                                      TABLE 19                                     __________________________________________________________________________     Herbicidal Activity Test                                                       __________________________________________________________________________     Herbicide:  EPTAM ® = S-ethyl N,N-di-n-propyl thiocarbamate                Antidote Nos.:                                                                             Keyed to Table 18                                                  Extender:   O,O-diethyl-O-phenyl phosphorothioate                              Evaluation Time:                                                                           Three weeks after 2nd treatment                                    Application Rate:                                                                          As shown                                                           __________________________________________________________________________                                 % Control of Weeds 3                                        Second Treatment (6 Weeks                                                                         Weeks After Second                                          After the First)   Treatment                                          1st Treatment                                                                           EPTAM  Antidote                                                                              Extender                                                                            Water                                                                              Green                                                                              Wild                                       EPTAM ® lb/A                                                                        lb/A + at 1 lb/A                                                                           + lb/A grass                                                                              Foxtail                                                                            Cane                                       __________________________________________________________________________     0        0      0      0    0   0   0                                          0        3      0      0    94  95  98                                         3        3      0      0    0   0   3                                          3        3      0      4    96  85  97                                         3        3      1      0    0   0   0                                          3        3      1      4    95  75  95                                         3        3      2      0    0   0   0                                          3        3      2      4    97  80  98                                         3        3      3      0    0   0   0                                          3        3      3      4    70  80  92                                         3        3      4      0    0   0   0                                          3        3      4      4    97  80  90                                         3        3      5      0    0   0   0                                          3        3      5      4    98  85  100                                        __________________________________________________________________________

EXAMPLE 10 Tests with Extender in Pretreated Soil

The extender O,O-diethyl O-phenyl phosphorothioate was tested alone at 4 and 8 lb/A in soil pretreated with a thiocarbamate. This example differs from that of Example 8 where the extender was tested alone at 2 and 4 lb/A in non-conditioned soil, meaning the soil had not been pretreated.

These tests were run concurrently with those recorded in Example 9. The same procedures were followed except that only 10 ml of the extender alone was incorporated into the soil pretreated with EPTAM® six weeks earlier.

The results, recorded in Table 20, indicate that at 4 and 8 lb/acre the extender exhibited no herbicidal activity whatsoever in soil pretreated with EPTAM®.

                                      TABLE 20                                     __________________________________________________________________________     Herbicidal Activity Test - Extender Alone                                      __________________________________________________________________________     Extender:        O,O-diethyl O-phenyl phosphorothioate                         Application Rate:                                                                               4 and 8 lb/A                                                  Evaluation Time: Three weeks after 2nd treatment                               __________________________________________________________________________                                 % Control of Weeds 3                                        Second Treatment 6 Weeks                                                                          Weeks After Second                                          After the First    Treatment                                          1st Treatment                                                                           EPTAM  Antidote                                                                              Extender                                                                            Water                                                                              Green                                                                              Wild                                       EPTAM ® lb/A                                                                        lb/A + at 1 lb/A                                                                           + lb/A grass                                                                              Foxtail                                                                            Cane                                       __________________________________________________________________________     0        0      0      0    0   0   0                                          3        0      0      4    0   0   0                                          3        0      0      8    0   0   0                                          __________________________________________________________________________

EXAMPLE 11 Herbicidal Activity of Several Different Thiocarbamates

This example provides data much like that of Example 10 above, and essentially follows the procedures therein described. Sandy loam soil from San Jose, Calif. was used in these tests. It was pretreated to simulate previous herbicide applications.

The thiocarbamate herbicide which was tested according to the procedure described below was S-ethyl-N-ethyl-N-cylohexyl thiocarbamate (RO-NEET®).

A: Soil Pre-Treatment

A stock solutions of the thiocarbamate herbicide was prepared as follows: 149.4 mg of an emulsifiable liquid concentrate of RO-NEET® containing 6 lb/gal (0.72 kg/l) (74.3% by weight of the herbicide) was suspended as an emulsion in 100 ml of water.

The sandy loam soil was measured out to fill aluminum flats 8.5×6.0×1.75 inches (22×15×4.5 cms). The soil was then emptied from each flat individually into a 5-gallon rotary mixer. Ten ml of the thiocarbamate stock solution was then pipetted and placed into the rotary mixer where it was incorporated. The soil was then replaced in the flat. The application rate provided by 10 ml was calculated as 3 lb/A of the herbicide.

Each flat was then planted with two rows of watergrass (Echinochloa crus-galli) and one row each of johnsongrass (Sorghum haliepense), wild oats (Avena fatua) and milo (Sorghum bicolor). The flats were placed in the greenhouse at 70°-95° F. and watered daily by sprinkling.

Two months later, the plants and roots were removed by sieving. The soil was replaced in the flats.

B. Herbicide Test

The RO-NEET® stock solution preparation described in Part (A) was formulated again. An additional stock solution of the organophosphorus extender compound was prepared as follows:

38.7 mg of technical grade, O,O-diethyl-O-phenyl phosphorothioate was combined with 5 cc of acetone, 95 ml of water, and 0.2 ml of an emulsifier/surfactant. Ten ml of the last stock solution translated to 1 lb/A when applied to a flat of soil.

Two flats as in Part (A) above were filled with soil treated as in Part (A). Incorporated into one flat's worth of pretreated soil by rotary mixing was a 20 ml tank-mix comprising 10 ml of the RO-NEET® stock solution and 10 ml of the extender stock solution. Incorporated into another flat's worth of pretreated soil was just 10 ml of RO-NEET® stock solution alone.

Incorporated into the flat of non-pretreated soil was 10 ml of the RO-NEET® stock solution. One flat of non-pretreated soil was left untreated at the time for second soil treatment as an untreated control flat.

The weed control ratings, measured as in Example 1 above, were taken 15 days after the second treatment and are recorded in Table 22 below. The results show that adding the representative organophosphorus extender O,O-diethyl-O-phenyl-phosphorothioate extended the herbicidal activity of RO-NEET® when tested upon re-treatment. An untreated control flat provides the first line of data in Table 22.

                                      TABLE 22                                     __________________________________________________________________________     Herbicidal Activity of Several different thiocarbamates Improved by the        Extender: O,O-diethyl O-phenyl phosphorothioate                                __________________________________________________________________________            Application Rate:                                                                              As indicated in terms of lb/A                                  Application Method:                                                                            Pre-plant incorporation                                 __________________________________________________________________________             Second Soil Treatment, PPI*                                            First Soil       Extender                                                                            Water                                                                              Wild                                                                              Johnson                                                                             Wild                                         Treatment                                                                              Herbicide                                                                            lb/A                                                                              lb/A grass*                                                                             cane                                                                              grass                                                                               oats                                                                               Sorghum                                  __________________________________________________________________________           0 0     0  0    0   0  0    0   0                                              0 RO-NEET                                                                              3  0    83  75 90   100 75                                       RO-NEET                                                                              3 RO-NEET                                                                              3  0    73  30 20   85  10                                       RO-NEET                                                                              3 RO-NEET                                                                              3  1    81  90 100  100 97                                       __________________________________________________________________________      *Results shown for watergrass are an average of two replications.        

EXAMPLE 12 Further Tests Indicating Herbicidal Activity Improvement with Herbicide, Extender and Antidote Compositions

This example offers herbicidal activity test data demonstrating the effectiveness of representative organophosphorus extender compounds in prolonging the herbicidal activity of compositions containing a thiocarbamate herbicide and a representative antidote of the instant invention. The effect is observed by comparing the extent of weed control in test flats treated with a thiocarbamate and antidote composition only against the weed control occurring in similar flats treated with compositions containing a thiocrbamate herbicide, an antidote and an organophosphorus extender. The soil used in these tests was a sandy loam soil from San Jose, Calif., which was pre-treated with a thiocarbamate herbicide to simulate a typical field which had received previous herbicide applications.

A. Soil Pre-Treatment

A solution was prepared by diluting an emulsifiable liquid concentrate containing 6 lb/gal (0.72 kg/l) (76.8% by weight) of the herbicide S-ethyl di-n-propylthiolcarbamate in 200 ml of water, such that the resulting concentration of herbicide in the solution was 2000 mg/l. Two hundred ml of this solution was then added to 200 lb (90.8 kg) of soil and the mixture was mixed in a rotary mixer for thirty minutes. Also added was 17-17-17 fertilizer (N-P₂ O₅ -K₂ O on a weight basis), amounting to 50 ppm by weight with respect to the soil.

The soil was then placed in round plastic containers, 7.5 inches (19.0 cm) in diameter by 7.5 inches (19.0 cm) deep. The soil was tamped and leveled with a row marker to impress three rows across the width of each container. One row was seeded with DeKalb XL-45A corn (Zea mays), and two rows were seeded with barnyardgrass (Echinochloa crus-galli). Sufficient seeds were planted to produce several seedlings per inch of row. The containers were then placed in a greenhouse maintained at 20° C. to 30° C. and watered daily by sprinkler.

Five weeks after treatment, the soil was allowed to dry out and the plant foliage was removed. The soil was then passed through a 0.25 inch (0.64 cm) screen to remove plant roots and clods, and then passed through a 2 millimeter (mm) screen.

B. Herbicide Test

Stock solutions for the tests recorded in Table 23 were prepared by adding to 100 cc of water such amounts of emulsifiable liquid concentrates of an organophosphorus extender compound or of a composition comprising a thiocarbamate herbicide and a representative antiodote of the instant invention such that 5 cc of the resulting mixture when added to three pounds of soil yielded a quantity of soil equivalent to the desired application rate expressed in pounds per acre. Stock solutions for the tests recorded in Table 24 were prepared as just indicated and in addition another stock solution was prepared by adding such amounts of a technical grade organophosphorus extender compound to 100 cc mixture of equal parts of water and acetone such that 5 cc of the resulting mixture when added to three pounds of soil would also yield the desired application rate. Then either 5 cc of a stock solution containing a thiocarbamate herbicide and an antidote or 10 cc of a tank-mix comprising 5 cc of the thiocarbamate and antidote stock solution and 5 cc of an organophosphorus extender stock solution were incorporated into three pounds of soil in a rotary mixer.

The treated soil was then placed in aluminum flats which were approximately 3 inches deep, 6 inches wide and 9 inches long (8×15×23 cm). The soil was tamped and leveled with a row marker to impress six rows across the width of the flat. The test weeds employed in the tests recorded in Table 23 were as follows:

    ______________________________________                                         COMMON NAME      SCIENTIFIC NAME                                               ______________________________________                                         watergrass       Echinochloa crus-galli (L.)                                   wild oats        Avena fatua (L.)                                              wild cane        Sorghum bicolor (L.) Moench                                   green foxtail    Setaria viridis (L.) Beauv.                                   ______________________________________                                    

The same weed species were employed in the tests recorded in Table 24 with the addition of annual ryegrass (Lolium multiflorum). In both series of tests, milo [(Sorghum bicolor (L.) Moench] was included as a plant growth indicator.

Sufficient seeds were planted to produce several seedlings per inch in each row. The flats were then placed in a greenhouse maintained at 70° to 85° F. (21° to 30° C.) and watered daily by sprinkler.

Approximately three weeks after treatment, the degree of weed control and corn injury were estimated and recorded as percentage control compared to the growth of the same species in an untreated check flat of the same age. The rating scale ranges from 0 to 100%, where 0 equals no effect with plant growth equal to the untreated control, and 100 equals complete kill.

The thiocarbamates tested were as follows:

EPTAM=S-ethl-N,N-dipropyl thiocarbamate

SUTAN=S-ethyl-N,N-diisobutyl thiocarbamate

VERNAM=S-propyl-N,N-dipropyl thiocarbamate

The antidotes tested were:

A-1=N,N-diallyl-dichloroacetamide

A-2=2,2,5-trimethyl-N-dichloroacetyl oxazolidine

The organophosphorus extender compounds tested were:

Ex-1=O,O-diethyl-O-phenyl phosphorothioate

EX-2=O,O-diethyl-O-benzyl phosphorothioate.

Table 23 and Table 24 indicate that representative organophosphorus extender compounds prolong the herbicidal activity of thiocarbamate herbicide compositions containing a representative antidoate.

                                      TABLE 23                                     __________________________________________________________________________     Herbicidal Activity Tests of 3-Component Compositions                          __________________________________________________________________________     Antidote:      A-2 = 2,2,5-Trimethyl N-dichloroacetyl oxazolidine              Extender:      EX-1 = O,O-Diethyl-O-phenyl phosphorothioate                    __________________________________________________________________________     TREATMENT                                                                              Application Application Application                                                                           Ave. %                                  Herbicide                                                                              Rate (lb/A)                                                                           Antidote                                                                            Rate (lb/A)                                                                           Extender                                                                            Rate (lb/A)                                                                           Control                                 __________________________________________________________________________       SUTAN 3.0    A-2  0.06   --   --     33%                                       SUTAN 6.0    A-2  0.12   --   --     42%                                       SUTAN 3.0    A-2  0.06   EX-1 0.50   75%                                       SUTAN 6.0    A-2  0.12   EX-1 1.00   88%                                       EPTAM 3.0    A-2  0.12   --   --     6%                                        EPTAM 6.0    A-2  0.25   --   --     12%                                       EPTAM 3.0    A-2  0.12   EX-1 0.50   34%                                       EPTAM 6.0    A-2  0.25   EX-1 1.00   47%                                       VERNAM                                                                               3.0    A-2  0.12   --   --     5%                                      10.                                                                              VERNAM                                                                               6.0    A-2  0.25   --   --     23%                                       VERNAM                                                                               3.0    A-2  0.12   EX-1 0.50   78%                                       VERNAM                                                                               6.0    A-2  0.25   EX-1 1.00   93%                                     __________________________________________________________________________

                                      TABLE 24                                     __________________________________________________________________________     Further Herbicidal Activity Tests of 3-Component Compositions                  __________________________________________________________________________     Antidote:      A-1 = N,N-diallyl dichloroacetamide                             Extender:      EX-2 = O,O-Diethyl-O-benzyl phosphorothioate                    __________________________________________________________________________     TREATMENT                                                                             Application Application Application                                                                           Ave. %                                   Herbicide                                                                             Rate (lb/A)                                                                           Antidote                                                                            Rate (lb/A)                                                                           Extender                                                                            Rate (lb/A)                                                                           Control                                  __________________________________________________________________________       EPTAM                                                                               3.0    A-1  0.25   --   --     3%                                         EPTAM                                                                               6.0    A-1  0.50   --   --     73%                                        EPTAM                                                                               3.0    A-1  0.25   EX-2 0.50   88%                                        EPTAM                                                                               3.0    A-1  0.25   EX-2 0.50   80%                                        EPTAM                                                                               6.0    A-1  0.50   EX-2 1.00   90%                                        EPTAM                                                                               6.0    A-1  0.50   EX-2 1.00   91%                                        SUTAN                                                                               3.0    A-1  0.125  --   --     69%                                        SUTAN                                                                               6.0    A-1  0.25   --   --     95%                                        SUTAN                                                                               3.0    A-1  0.125  EX-2 0.50   100%                                     10.                                                                              SUTAN                                                                               3.0    A-1  0.125  EX-2 0.50   99%                                        SUTAN                                                                               6.0    A-1  0.25   EX-2 1.00   100%                                       SUTAN                                                                               6.0    A-1  0.25   EX-2 1.00   100%                                     __________________________________________________________________________

EXAMPLE 13 Further Herbicidal Activity Tests of 3-Component Compositions

Further tests comparing the herbicidal activity of thiocarbamate herbicide and dihaloacetamide antidote compositions in soil preteated with a thiocarbamate and the herbicidal activity of such compositions also comprising an extender were conducted according to the following procedures. These tests were similar to those of Example 7 except that they were run at different application rates of the components. The weight ratio of thiocarbamate to the antidote herein is 12:1. The weight ratio of the thiocarbamate to the extender herein is 6:1.

The following two antidotes were employed in these tests:

Antidote Compound No. 5 (structure in Table 18 above)=N-allyl-N-[2-(1,3-dioxolanyl)]-methyl dichloroacetamide;

Antidote Compound No. 6=N,N-diallyl dichloroacetamide ##STR53##

A. Soil Pre-Treatment

The same procedure as in Example 7, Part (A) was employed. The soil was thereby pretreated with S-ethyl N,N-di-n-propyl thiocarbamate at 3 lb/A.

B. Herbicide Test

The following stock solutions were prepared:

1. 120 mg of technical grade S-ethyl N,N-di-n-propyl thiocarbamate was dissolved in 50 ml of water and 50 ml of acetone such that 6.7 ml of the resulting mixture when added to three pounds of soil yielded an application rate of 4 lb/acre;

2. 144 mg of an emulsifiable concentrate containing 83% S-ethyl N,N-di-n-propyl thiocarbamate and 6.9% N,N-diallyl dichloroacetamide (hereinafter Antidote #6) was dissolved in 100 ml of water such that 6.7 ml when combined with 3 pounds of soil yielded an application rate of 4 lb/Acre of the herbicide and 0.3 lb/A of the antidote;

3. 60 mg of technical grade N-allyl-N-[2-(1,3-dioxolanyl)]methyl dichloroacetamide (hereinafter Antidote #5) was dissolved in 50 ml of acetone and 50 ml of water such that 1.3 ml combined with 3 pounds of soil yielded an application rate of 0.3 lb/A;

4. 108 mg of technical grade O,O-diethyl O-phenyl phosphorothioate was dissolved in 50 ml of acetone and 50 ml of water such that 1.3 ml when combined with 3 pounds of soil yielded an application rate of 0.67 lb/A.

Apporopriate amounts of the stock solutions were then incorporated in the soil either alone or in a tank-mix with other components depending on the treatment for the particular flat.

The treated soil was then placed in aluminum flats which were 2.5 inches deep, 3.5 inches wide and 7.5 inches long (6.4×8.9×19.0 cm). The soil was tamped and leveled with a row marker to impress six rows across the width of the flat.

The same weed species and plant growth indicators as used in Example 7 above were employed except green foxtail (Setaria viridis) was employed rather than yellow foxtail.

The flats were then placed in a greenhouse maintained at 70° to 85° F. and watered daily by sprinklers. The visual weed control ratings were taken two weeks after the intial treatment.

The results recorded in Table 25 are each the average of two replications except for results asterisked (*) indicating an average of four replications. The results show that the addition of a representative extender to a thiocarbamate and herbicide composition extends the herbicidal activity of such compositions.

                  TABLE 25                                                         ______________________________________                                         Further Herbicidal Activity Tests of 3-Component Compositions                  ______________________________________                                         Herbicide:                                                                              S-ethyl N,N-di-n-propyl thiocarbamate                                          (EPTAM ®)                                                         Antidote:                                                                               A-5 = N-allyl-N-[2-(1,3-dioxolanyl)]-methyl                                    dichloroacetamide                                                              A-6 = N,N-diallyl dichloroacetamide                                   Extender:                                                                               O,O-diethyl-O-phenyl phosphorothioate                                 Evaluation:                                                                             3 weeks after treatment                                               Soil     3 lb EPTAM ®                                                      Pretreatment:                                                                  ______________________________________                                         Treatment                                                                      EPTAM ®                  Extender                                          Application       Application                                                                               Application                                                                             Avg. %                                   Rate (lb/A)                                                                             Antidote Rate (lb/A)                                                                               Rate (lb/A)                                                                             Control                                  ______________________________________                                         0        A-5      0.3        0        0                                        0        A-5      0.5        0        0                                        0        A-5      0.7        0        0                                        4        A-5      0.3        0        12*                                      6        A-5      0.5        0        36*                                      9        A-5      0.7        0        50.5*                                    4        A-5      0.3        0.67     34                                       6        A-5      0.5        1.0      62                                       9        A-5      0.7        1.5      78                                       4        A-6      0.3        0        0                                        6        A-6      0.5        0        23                                       9        A-6      0.7        0        26                                       4        A-6      0.3        0.67     27                                       6        A-6      0.5        1.0      72                                       9        A-6      0.7        1.5      77                                       ______________________________________                                    

METHODS OF APPLICATION

The herbicidal compositions of the present invention are useful in controlling the growth of undersirable vegetation by pre-emergence or post-emergence application to the locus where control is desired, including pre-plant and post-plant soil incorporation as well as surface application. The compositions are generally embodied in formuations suitable for convenient application. Typical formulations contain additional ingredients or diluent carriers which are either inert or active. Examples of such ingredients or carriers are water, organic solvents, dust carriers, granular carriers, surface active agents, oil and water, water-oil emulsions, wetting agents, dispersing agents, and emulsifying agents. The herbicidal formulations generally take the form of dusts, emulsifiable concentrates, granules and pellets, or microcapsules.

A. DUSTS

Dusts are dense powder compositions which are intended for application in dry form. Dusts are characterized by their free-flowing and rapid settling properties so that they are not readily windborne to areas where their presence is not desired. They contain primarily an active material and a dense, free-flowing, solid carrier.

Their performance is sometimes aided by the inclusion of a wetting agent, and convenience in manufacture frequently demands the inclusion of an inert, absorptive grinding aid. For the dust compositions of this invention, the inert carrier may be either of vegetable or mineral origin, the wetting agent is preferably anionic or nonionic, and suitable absorptive grinding aids are of mineral origin.

Suitable classes of inert solid carriers for use in the dust compositions are those organic or inorganic powders which possess high bulk density and are very free-flowing. They are also characterized by low surface area and poor liquid absorptivity. Suitable grinding aids are natural clays, diatomaceous earth, and synthetic mineral fillers derived from silica or silicate. Among ionic and nonionic wetting agents, the most suitable are the members of the group known to the art as wetting agents and emulsifiers. Although solid agents are preferred because of ease in incorporation some liquid nonionic agents are also suitable in the dust formulation.

Preferred dust carriers are micaceous talcs, pyrophyllite, dense kaolin clays, tobacco dust and ground calcium phosphate rock.

Preferred grinding aids are attapulgite clay, diatomaceous silica, synthetic fine silica and synthetic calcium and magnesium silicates.

Most preferred wetting agents are alkylbenzene and alkylnaphthalene sulfonates, sulfated fatty alcohols, amines or acid amides, long chain acid esters of sodium isothionate, esters of sodium sulfosuccinate, sulfated or sulfonated fatty acid esters, petroleum sulfonates, sulfonated vegetable oils, and ditertiary acetylenic glycols. Preferred dispersants are methyl cellulose, polyvinyl alcohol, lignin sulfonates, polymeric alkylnaphthalene sulfonates, sodium naphthalenesulfonate, polymethylene bisnaphthalenesulfonate, and sodium-N-methyl-N-(long chain acid) taurates.

The inert solid carriers in the dusts of this invention are usually present in concentrations of from about 30 to 90 weight percent of the total composition. The grinding aid will usually constitute 5 to 50 weight percent of the compositions, and the wetting agent will constitute from about 0 to 1.0 weight percent of the composition. Dust compositions can also contain other surfactants such as dispersing agents in concentrations of up to about 0.5 weight percent, and minor amounts of anticaking and antistatic agents. The particle size of the carrier is usually in the range of 30 to 50 microns.

B. EMULSIFIABLE CONCENTRATE

Emulsifiable concentrates are usually solutions of the active materials in nonwater-miscible solvents together with an emulsifying agent. Prior to use, the concentrate is diluted with water to form a suspended emulsion of solvent droplets.

Typical solvents for use in emulsifiable concentrates include weed oils, chlorinated hydrocarbons, and nonwater-miscible ethers, esters, and ketones.

Typical emulsifying agents are anionic or nonionic surfactants, or mixtures of the two. Examples inlcude long-chain alkyl or mercaptan polyethoxy alcohols, alkylaryl polyethoxy alcohols, sorbitan fatty acid esters, polyoxyethylene ethers with sorbitan fatty acid esters, polyoxyethylene glycol esters with fatty or rosin acids, fatty alkylol amide condenstes, calcium and amine salts of fatty alcohol sulfates, oil soluble petroleum sulfonates or, preferably mixtures of these emulsifying agents. Such emulsifying agents will comprise from about 1 to 10 weight percent of the total composition.

Thus, emulsifiable concentrates of the present invention will consist of from about 15 to about 50 weight percent active material, about 40 to 82 weight percent solvent, and about 1 to 10 weight percent emulsifier. Other additivies such as spreading agents and stickers can also be included.

C. GRANULES AND PELLETS

Granules and pellets are physically stable, particulate compositions containing the active ingedients adhering to or distributed through a basic matrix of a coherent, inert carrier with macroscopic dimensions. A typical particle is about 1 to 2 millimeters in diameter. Surfactants are often present to aid in leaching of the active ingredients from the granule or pellet.

The carrier is preferably of mineral origin, and generally falls within one of two types. The first are porous, absorptive, performed granules, such as preformed and screened granular attapulgite or heat expanded, granular, screened vermiculite. On either of these, a solution of the active agent can be sprayed and will be absorbed at concentrations up to 25 weight percent of the total weight. The second, which are also suitable for pellets, are initially powdered kaolin clays, hydrated attapulgite, or bentonite clays in the form of sodium, calcium or magnesium bentonites. Water-soluble salts, such as sodium salts, may also be present to aid in the disintegration of granules or pellets in the presence of moisture. These ingredients are blended with the active components to give mixtures that are granulated or pelleted, followed by drying, to yield formulations with the active component distributed uniformly throughout the mass. Such granules and pellets can also be made with 25 to 30 weight percent active component, but more frequently a concentration of about 10 weight percent is desired for optimum distribution. The granular compositions of this invention are most useful in a size range of 15-30 mesh.

The surfactant is generally a common wetting agent of anionic or nonionic character. The most suitable wetting agents depend upon the type of granule used. When preformed granules are sprayed with active material in liquid form the most suitable wetting agents are nonionic, liquid wetters miscible with the solvent. These are compounds more generally known to the art as emulsifiers, and comprise alkylaryl polyether alcohols, alkyl polyether alcohols, polyoxyethylene sorbitan fatty acid esters, polythylene glycol esters with fatty or rosin acids, fatty alkylol amide condensates, oil solution petroleum or vegetable oil sulfonates, or mixtures of these. Such agents will usually comprise up to about 5 weight percent of the total composition.

When the active ingredient is first mixed with a powdered carrier and subsequently granulated, or pelleted, liquid nonionic wetters can still be used, but it is usually preferable to incorporate at the mixing stage one of the solid, powdered anionic wetting agents such as those previously listed for the wettable powders. Such agents will comprise from about 0 to 2 weight percent of the total composition.

Thus, the preferred granular or pelleted formulations of this invention comprise about 5 to 30 weight percent active material, about 0 to 5 weight percent wetting agent, and about 65 to 95 weight percent inert material carrier, as these terms are used herein.

D. MIRCOCAPSULES

Microcapsules consist of fuly enclosed droplets or granules containing the active materials, in which the enclosing material is an inert porous membrane, arranged to allow escape of the enclosed materials to the surrounding medium at controlled rates over a specified period. Microcapsules are particularly useful in the present invention since the organophosphorus compounds of the herbicide composition are liquid.

Encapsulated droplets are typically about 1 to 50 microns in diameter. The enclosed liquid typically constitutes about 50 to 95% of the weight of the entire capsule, and may contain a small amount of solvent in addition to the active materials.

Encapsulated granules are characterized by porous membranes sealing the openings of the granule carrier pores, trapping the liquid containing the active components inside for controlled release. A typical granule size ranges from 1 millimeter to 1 centimeter in diameter. In agricultural usage, the granule size is generally about 1 to 2 millimeters in diameter. Granules formed by extrusion, agglomeration, or prilling, are useful in the present invention as well s materials in their naturaly occurring form. Examples of such carriers are vermiculite, sintered clay granules, kaolin, attapulgite clay, sawdust, and granular carbon.

Useful encapsulating materials include natural and synthetic rubbers, cellulosic materials, styrene-butadiene copolymers, polyacrylonitriles, polyacrylates, polyesters, polyamides, poylurethanes, and starch xanthates.

E. INJECTION WITH ANHYDROUS AMMONIA

The herbicidal compositions of the instant invention comprising a thiocarbamate herbicide, organophosphorus extender and optionally an antidote can be applied to the soil by in-line injection with anhydrous ammonia. For pre-emergence soil injection applications of anhydrous ammonia, on conservation or conventional tilled acreage, the herbicidal composition of the instant invention can be introduced into the anhydrous line using a metering pump which offers a constant rate of the output per acre independent of the anhydrous ammonia output rate. The herbicidal composition discharge hose can tee into the ammonia discharge line between the meter and the manifold. Injection depth can be from 4 to 5 inches. The herbicidal compositions can also be injected with anhydrous ammonia in no-till situations.

Other herbicide products can be surface applied and incorporated at the same time the herbicidal compositions of the instant invention and anhydrous ammonia are injected, or post-emergent applications can be used.

F. IN GENERAL

Many of the above formulations can be prepred as a package containing both the thiocarbamate herbicide and the organophosphorus extender together with the other ingredients of the formulation (diluents, emulsifiers, surfactants, etc.). The formulations can also be prepred by a tank mix method, in which the ingredients are obtained separately and combined at the grower site. The herbicide and extender may both be used in the same type of formulation or a different formulation maybe used for each, e.g., the herbicide may be in microcapsule form while the extender may be an emulsifiable concentrate, or vice versa.

As a further alternative, the herbicide and extender can be applied sequentially, with either being applied first. This is a less preferred method, however, since more effective results are obtained with simultaneous application.

In general, any conventional method of application can be used. The locus of application can be soil, sees, seedlings, or the actual plants, as well as flooded fields. Soil application is preferred. Dusts and liquid compositions can be applied by the use of powder dusters, boom and hand sprayers, and spray dusters. The compositions can also be applied from airplanes as dusts or sprays because they are effective in very low dosages. In order to modify or control the growth of germinating seeds or emerging seedlings, as a typical example, the dust and liquid compositions are applied to the soil according to conventional methods and are distributed in the soil to a depth of at least one-half inch below the soil surface. It is not necessary that the phytotoxic compostions be admixed with the soil particles. Instead, these compositions can be applied merely by spraying or sprinkling the surface of the soil. The phytotoxic compositions of this invention can also be applied by additionn to irrigation water supplied to the field to be treated. This method of application permits the penetration of the compositions into the soil as the water is absorbed therein. Dust compositions, granular compositions or liquid formulations applied to the surface of the soil can be distributed below the surfacae of the soil by conventional means such as discing, dragging or mixing operations.

The herbicide/extender compositions can also be applied to the soil through irrigation systems. According to this technique, the compositions are added directly to irrigation water immediately prior to irrigation of the field. This technique is applicable in all geographical areas regardless of rainfall, since it permits supplementation of the natural rainfall at critical stages of plant growth. In a typical application, the concentration of the herbicide/extender composition in the irrigation water will range from about 10 to 150 parts per million by weight. The irrigation water can be applied by the use of sprinkler systems, surface furrows, or flooding. Such application is most effectively done before the weeds germinate, either early in the spring prior to germination or within two days after cultivation of the field.

The compositions of this invention can also contain further additaments, such as fertilizers, insecticides, or other herbicides. Suitable pesticides include 2,4-dichlorophenoxyacetic acids, 2,4,5-trichlorophenoxy acetic acid, 2-methyl-4-chlorophenoxyacetic acid, and the salts, esters and amides thereof; triazine derivatives, such as 2,4-bis(3-methoxypropylamino)-6-methyl-thio-s-triazine, 2-chloro-4-ethylamino-6-isopropylamino-s-triazine, 2-ethylamino-4-isopropylamino-6-methylmercapto-s-triazine; urea derivatives such as 3-(3,4-dichlorophenyl)-1,1dimethyl urea; acetamides such as N,N-diallyl-α-chloroacetamide, N-(α-chloroacetyl) hexamethyleneimine, and N,N-diethyl-α-bromoacetamide; and benzoic acids such a 3-amino-2,5-dichlorobenzoic acid. Fertilizers useful in combination with the active ingredients include ammonium nitrate, urea, and superphosphate. Other useful additaments include materials in which plant organisms take root and grow, such as compost, manure, humus, sand and the like.

The amount of composition of the present invention which constitutes a herbicidally effective amount depends upon the nature of the seeds or plants to be controlled. The rate of application of active ingredient varies from about 0.01 to about 50 pounds per acre, preferably about 0.1 to about 25 pounds per acre with the actual amount used depending on the overall cost and the desired results. It sill be readily apparent to one skilled in the art that compositions exhibiting lower herbicidal activity will require a higher dosage rate for the same degree of control than more active compounds. 

What is claimed is:
 1. An herbicidal composition comprising(a) an herbicidally effective amount of a thiolcarbamate having the formula ##STR54## in which R¹ is C₁ -C₆ alkyl, R² is C₁ -C₆ alkyl, R³ is C₁ -C₆ alkyl or cyclohexyl; and (b) an alkyl thiolcarbamate herbicide soil-life-extending non-phytotoxic amount of an organophosphorus compound having the formula ##STR55## in which Y is oxygen or sulfur; R⁴ is C₁ -C₆ alkyl, optionally substituted with halo, or is C₃ -C₆ alkenyl optionally substituted with cyano; R⁵ is C₁ -C₄ alkyl, straight-chain C₁ -C₆ alkoxy or C₁ -C₄ alkylthio other than tertiary butylthio; R⁶ is C₁ -C₄ alkyl substituted with one C₁ -C₃ alkylthio group; C₅ -C₇ cycloalkyl; C₁ -C₄ alkylimino optionally substituted with one, two or three halogen atoms; phenyl optionally substituted with nitro, ortho-nitro and halo, C₁ -C₃ alkylsulfinyl, α-pentynyl, or trifluoromethyl; benzyl optionally substituted with halo; or is -(R⁷)-φ in whichR⁷ is C₁ -C₄ alkylene substituted with either cyano or with one, two or three halogen atoms; and φ is phenyl substituted with halo when R₇ is substituted with cyano but is phenylthio subsituted with halo with R₇ is substituted with one, two or three halogen atoms; X is oxygen or sulfur; with the provisos that: when R⁴ is C₁ -C₆ alkyl, R⁴ is other than tertiary butyl; when R⁶ is C₅ -C₇ cycloalkyl, substituted or unsubstituted phenyl, or substituted or unsubstituted benzyl, then X must be oxygen; when R⁴ is allyl, Y is oxygen, and R⁶ is para-nitrophenyl, then R⁵ is other than methyl; and when R⁴ is methyl and R⁶ is phenyl, then R⁵ is other than C₁ -C₄ alkylthio or ethoxy.
 2. An herbicidal composition according to claim 1 whereinR⁴ is C₁ -C₆ alkyl, other than tertiary butyl, optionally substituted with halo; R⁵ is ethyl, straight-chain C₁ -C₄ alkoxy, or C₁ -C₄ alkylthio other than tertiary butylthio; R⁶ is C₅ -C₇ cycloalkyl, benzyl or phenyl optionally substituted with either halo, or ortho-nitro and halo; and X is oxygen.
 3. An herbicidal composition according to claim 1 whereinR⁴ is ethyl, n-propyl, or n-butyl; R⁵ is methoxy, ethoxy, n-propoxy, ethylthio, or n-propylthio; R⁶ is C₅ -C₇ cycloalkyl, benzyl or phenyl optionally substituted with halo; X is oxygen; with the provision that wherein Y is sulfur, R⁴ is ethyl, n-propyl or n-butyl and R⁶ is phenyl, R₅ is other than methoxy.
 4. An herbicidal composition according to claim 1 wherein the organophosphorus compound is O,O-diethyl-O-phenyl phosphorothioate.
 5. An herbicidal composition according to claim 4 wherein the thiocarbamatae is S-ethyl N,N-di-n-propyl thiocarbamate.
 6. An herbicidal composition according to claim 4 wherein the thiocarbamate is S-ethyl N,N-diisobutyl thiocarbamate.
 7. An herbicidal composition according to claim 4 wherein the thiocarbamate is S-propyl N,N-dipropyl thocarbamate.
 8. An herbicidal composition according to claim 1 wherein the organophosphorous compound is O,O-diethyl-O-benzyl phosphorothioate.
 9. An herbicidal composition according to claim 1 wherein the organophosphorus compound is O-ethyl-O-phenyl-S-n-propyl phosphorodithioate.
 10. An herbicidal composition according to claim 1 wherein the organophosphorus compound is O-ethyl-S-ethyl-O-phenyl phosphorothioate.
 11. An herbicidal composition according to claim 1 wherein the organophosphorus compound is O-ethyl-O-phenyl-S-n-buty phosphorothioate.
 12. An herbicidal composition according to claim 1 wherein the weight ratio of said thiocarbamate to said organophosphorus compound is from about 1:1 to about 25:1.
 13. An herbicidal composition according to claim 1 wherein the weight ratio of said thiocarbamate to said organophosphorus compound is from about 1:1 to about 15:1.
 14. A method of controlling undesirable vegetation comprising applying to the locus where control is desired both(a) an herbicidally effective amount of a thiolcarbamate having the formula ##STR56## in which R¹ is C₁ -C₆ alkyl, R² is C₁ -C₆ alkyl R³ is C₁ -C₆ alkyl or cyclohexyl; and (b) an alkyl thiolcarbamatae herbicide soil-life-extending non-phytotoxic amount of an organophosphorus compound having the formula ##STR57## in which Y is oxyen or sulfur; R⁴ is C₁ -C₆ alkyl, optionally substituted with halo, or is C₃ -C₆ alkenyl optionally substituted with cyano; R⁵ is C₁ -C₄ alkyl, straight-chain C₁ -C₆ alkoxy or C₁ -C₄ alkylthio other than tertiary butylthio; R⁶ is C₁ -C₄ alkyl substituted with one C₁ -C₃ alkylthio group; C₅ -C₇ cycloalkyl; C₁ -C₄ alkylimino optionally substituted with one, two or three halogen atoms; phenyl optionally substituted with nitro, ortho-nitro and halo, C₁ -C₃ alkylsulfinyl, α-pentynyl, or trifluoromethyl; benzyl optionally substituted with halo; or is -(R⁷)-φ in whichR⁷ is C₁ -C₄ alkylene substituted with either cyano or with one, two or three halogen atoms; and φ is phenyl substituted with halo when R₇ is substituted with cyano but is phenylthio substituted with halo when R₇ is substituted with one, two or three halogen atoms; X is oxygen or sulfur; with the provisos that: when R⁴ is C₁ -C₆ alkyl, R⁴ is other than teritary butyl; when R⁶ is C₅ -C₇ cycloalkyl, substituted or unsubstituted phenyl, or substituted or unsubstituted benzyl, then X must be oxygen; when R⁴ is allyl, Y is oxygen, and R⁶ is para-nitrophenyl, then R⁵ is other than methyl; and when R⁴ is methyl and R⁶ is phenyl, then R⁵ is other than C₁ -C₄ alkylthio or ethoxy. 